Loop prevention in virtual layer 2 networks

ABSTRACT

Techniques for loop prevention while allowing multipath in a virtual L2 network are described. In an example, a network virtualization device can generate a first L2 bridge protocol data unit by applying a first loop detection protocol specific to only the first port and the first host machine. The network virtualization device can transmit, to the first compute instance via the first port, a first frame that includes the first L2 BPDU. The network virtualization device can receive, from the first compute instance via the first port, a second frame. The network virtualization device can determine that the second frame comprises the first L2 BPDU. The network virtualization device can determine that a loop exists between the network virtualization device and the first compute instance based on the first loop detection protocol and the first L2 BPDU of the second frame.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit and is a continuation of applicationSer. No. 17/192,681 filed Mar. 4, 2021, entitled “LOOP PREVENTION INVIRTUAL LAYER 2 NETWORKS”, which claims benefit of U.S. ProvisionalApplication No. 63/031,325, filed on May 28, 2020, entitled “LOOPPREVENTION IN LAYER 2 VIRTUAL NETWORKS WITHOUT GLOBAL SPANNING TREEPROTOCOL,” which is incorporated by reference herein in its entirety forall purposes.

BACKGROUND

A cloud infrastructure, such as Oracle Cloud Infrastructure (OCI), canprovide a set of cloud services that enable entities (e.g., enterprises)subscribing to these services to build and run a wide range ofapplications and services in a highly available cloud-hostedenvironment. The subscribing entities are referred to as customers ofthe cloud services provider. A cloud infrastructure can offerhigh-performance compute, storage, and network capabilities in aflexible overlay virtual network that runs on top of the physicalunderlay network and that is securely accessible from an enterprise'son-premises network. A cloud infrastructure, such as OCI, generallyallows customers to manage their cloud-based workloads in the same waythey manage their on-premises workloads. Thus, organizations can get allthe benefits of the cloud with the same control, isolation, security,and predictable performance as their on-premises network.

Virtual networking is a foundation for cloud infrastructures and cloudapplications because virtual networking enables the ability to access,connect, secure, and modify cloud resources. Virtual networking enablescommunication between multiple computers, virtual machines (VMs),virtual servers, or other devices across different physical locations.While physical networking connects computer systems through cabling andother hardware, virtual networking uses software management to connectcomputers and servers in different physical locations over the Internet.A virtual network uses virtualized versions of traditional networkcomponents, such as network switches, routers, and adapters, allowingfor more efficient routing and easier network configuration andreconfiguration.

BRIEF SUMMARY

The present disclosure relates generally to virtual networking. Moreparticularly, techniques are described for loop prevention in virtualLayer 2 (L2) networks, while supporting multiple paths in such networks.According to certain embodiments, rather than using a global spanningtree protocol (STP), loops associated with virtual L2 networks may beprevented by enforcing certain rules in network interface cards (NICs)and/or using a lightweight, single-port STP. Various inventiveembodiments are described herein, including methods, systems,non-transitory computer-readable storage media storing programs, code,instructions executable by one or more processors, and the like.

According to certain embodiments, a method of loop prevention, whilesupporting multiple paths in a virtual L2 network may include receiving,by a network virtualization device (NVD) via a first port of the NVD, anL2 frame that includes a source media access control (MAC) address and adestination MAC address; associating the source MAC address with thefirst port of the NVD; and transmitting, by the NVD, the L2 frame via atleast a second port of the NVD, but not the first port of the NVD basedon a rule that prevents the transmitting using a port via which the L2frame was received. The NVD may provide instances of a virtual NIC(VNIC). The virtual L2 network may include an L2 virtual LAN (L2 VLAN).The first port may be connected to a host or a switch network, such as aClos switch network, that includes a plurality of switches.

According to certain embodiments, a further method of loop prevention,while supporting multiple paths in a virtual L2 network may involve alightweight, single-port STP that includes transmitting, via a firstport of a NVD, an L2 frame to a host executing a compute instance;receiving, via the first port of the NVD, the L2 frame from the host;determining, by the NVD, that the L2 frame is looped back; anddisabling, by the NVD, the first port of the NVD to stop transmittingand receiving frames using the first port.

According to certain embodiments, a non-transitory computer-readablememory may store a plurality of instructions executable by one or moreprocessors, the plurality of instructions comprising instructions thatwhen executed by the one or more processors cause the one or moreprocessors to perform any one of the above methods.

According to certain embodiments, a system may include one or moreprocessors, as well as a memory coupled to the one or more processors.The memory may store a plurality of instructions executable by the oneor more processors, the plurality of instructions comprisinginstructions that when executed by the one or more processors cause theone or more processors to perform any one of the above methods.

According to certain embodiments, a NVD may be configured to receive,via a first port of the NVD, an L2 frame that includes a source MACaddress and a destination MAC address; to associate the source MACaddress with the first port of the NVD; and to transmit the L2 frame viaat least a second port of the NVD, but not via the first port of the NVDbased on a rule that prevents the transmitting using a port via whichthe L2 frame was received. In some embodiments, the NVD may further beconfigured to transmit a Bridge Protocol Data Unit (BPDU) to a host of acompute instance via the first port of the NVD, receive the BPDU fromthe host by the first port of the NVD, determine that the BPDU is loopedback, and disable the first port of the NVD to stop transmitting andreceiving frames using the first port.

The terms and expressions that have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof. It is recognized,however, that various modifications are possible within the scope of thesystems and methods claimed. Thus, it should be understood that,although the present system and methods have been specifically disclosedby examples and optional features, modification and variation of theconcepts herein disclosed should be recognized by those skilled in theart, and that such modifications and variations are considered to bewithin the scope of the systems and methods as defined by the appendedclaims.

This summary is not intended to identify key or essential features ofthe claimed subject matter, nor is it intended to be used in isolationto determine the scope of the claimed subject matter. The subject mattershould be understood by reference to appropriate portions of the entirespecification of this disclosure, any or all drawings, and each claim.

The foregoing, together with other features and embodiments, will becomemore apparent upon referring to the following specification, claims, andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative examples are described in detail below with reference tothe following figures.

FIG. 1 is a high level diagram of a distributed environment showing avirtual or overlay cloud network hosted by a cloud service providerinfrastructure according to certain embodiments.

FIG. 2 depicts a simplified architectural diagram of the physicalcomponents in the physical network within CSPI according to certainembodiments.

FIG. 3 shows an example arrangement within CSPI where a host machine isconnected to multiple network virtualization devices (NVDs) according tocertain embodiments.

FIG. 4 depicts connectivity between a host machine and an NVD forproviding I/O virtualization for supporting multitenancy according tocertain embodiments.

FIG. 5 depicts a simplified block diagram of a physical network providedby a CSPI according to certain embodiments.

FIG. 6 illustrates an example of a virtual cloud network (VCN) thatincludes a virtual L2 network according to certain embodiments.

FIG. 7 illustrates an example of a VCN that includes L2 and virtual L3networks according to certain embodiments.

FIG. 8 illustrates an example of an infrastructure that supports avirtual L2 network of a VCN according to certain embodiments.

FIG. 9 illustrates an example of a loop between network virtualizationdevices (NVDs) according to certain embodiments.

FIG. 10 illustrates an example of preventing a loop between NVDsassociated with a virtual L2 network according to certain embodiments.

FIG. 11 illustrates an example of a loop between a NVD and a computeinstance executing on a host according to certain embodiments.

FIG. 12 illustrates an example of preventing a loop between a NVD and acompute instance executing on a host according to certain embodiments.

FIG. 13 depicts an example of a flow for preventing loops associatedwith a virtual L2 network.

FIG. 14 depicts an example of a flow for preventing loops between NVDsassociated with a virtual L2 network.

FIG. 15 depicts an example of a flow for preventing loops between a NVDand a compute instance associated with a virtual L2 network.

FIG. 16 is a block diagram illustrating one pattern for implementing acloud infrastructure as a service system, according to at least oneembodiment.

FIG. 17 is a block diagram illustrating another pattern for implementinga cloud infrastructure as a service system, according to at least oneembodiment.

FIG. 18 is a block diagram illustrating another pattern for implementinga cloud infrastructure as a service system, according to at least oneembodiment.

FIG. 19 is a block diagram illustrating another pattern for implementinga cloud infrastructure as a service system, according to at least oneembodiment.

FIG. 20 is a block diagram illustrating an example computer system,according to at least one embodiment.

DETAILED DESCRIPTION

The present disclosure relates generally to virtual networking, and moreparticularly, to techniques for preventing loops, while supportingmultiple paths in virtual Layer 2 (L2) networks. According to certainembodiments, loops in virtual L2 networks may be prevented by enforcingcertain rules that relate to using ports for transmitting frames and/orimplementing a lightweight spanning tree protocol (STP) per port.Various embodiments are described herein, including methods, systems,non-transitory computer-readable storage media storing programs, code,instructions executable by one or more processors, and the like.

A network may be susceptible to broadcast storms if loops areintroduced. A network may also need to include multiple paths (referredto herein as “multipath”) to provide redundant paths in case of a linkfailure. L2 switches may not natively allow multipath and may sufferfrom looping issues because L2 control protocols may not inherently haveloop prevention mechanisms. Generally, STP is usable to prevent loops inL2 networks. However, STP also prevents multipath and is typicallycomplex to implement. For instance, with STP, each switch or a networkvirtualization device (NVD) may need to implement logic for root bridgeselection or root bridge priorities and logic for root port (RP)selection or RP priorities across the various ports, and may need toselect a single path upon a loop detection.

According to some embodiments, the switch or NVD may implement certainrules to avoid loops at least between switches and/or NVDs, whileallowing multipath. In some embodiments, to avoid loops caused by asoftware bug, or more generally, software code of a compute instance ona host connected via a port, a lightweight STP may be implemented, wherethe lightweight STP may only need to manage the port connected to thehost and may not need to implement the logic for root bridge selectionor root bridge priorities and the logic for RP selection or RPpriorities.

Example Virtual Networking Architectures

The term cloud service is generally used to refer to a service that ismade available by a cloud services provider (CSP) to users or customerson demand (e.g., via a subscription model) using systems andinfrastructure (cloud infrastructure) provided by the CSP. Typically,the servers and systems that make up the CSP's infrastructure areseparate from the customer's own on-premise servers and systems.Customers can thus avail themselves of cloud services provided by theCSP without having to purchase separate hardware and software resourcesfor the services. Cloud services are designed to provide a subscribingcustomer easy, scalable access to applications and computing resourceswithout the customer having to invest in procuring the infrastructurethat is used for providing the services.

There are several cloud service providers that offer various types ofcloud services. There are various different types or models of cloudservices including Software-as-a-Service (SaaS), Platform-as-a-Service(PaaS), Infrastructure-as-a-Service (IaaS), and others.

A customer can subscribe to one or more cloud services provided by aCSP. The customer can be any entity such as an individual, anorganization, an enterprise, and the like. When a customer subscribes toor registers for a service provided by a CSP, a tenancy or an account iscreated for that customer. The customer can then, via this account,access the subscribed-to one or more cloud resources associated with theaccount.

As noted above, infrastructure as a service (IaaS) is one particulartype of cloud computing service. In an IaaS model, the CSP providesinfrastructure (referred to as cloud services provider infrastructure orCSPI) that can be used by customers to build their own customizablenetworks and deploy customer resources. The customer's resources andnetworks are thus hosted in a distributed environment by infrastructureprovided by a CSP. This is different from traditional computing, wherethe customer's resources and networks are hosted by infrastructureprovided by the customer.

The CSPI may comprise interconnected high-performance compute resourcesincluding various host machines, memory resources, and network resourcesthat form a physical network, which is also referred to as a substratenetwork or an underlay network. The resources in CSPI may be spreadacross one or more data centers that may be geographically spread acrossone or more geographical regions. Virtualization software may beexecuted by these physical resources to provide a virtualizeddistributed environment. The virtualization creates an overlay network(also known as a software-based network, a software-defined network, ora virtual network) over the physical network. The CSPI physical networkprovides the underlying basis for creating one or more overlay orvirtual networks on top of the physical network. The virtual or overlaynetworks can include one or more virtual cloud networks (VCNs). Thevirtual networks are implemented using software virtualizationtechnologies (e.g., hypervisors, functions performed by networkvirtualization devices (NVDs) (e.g., smartNICs), top-of-rack (TOR)switches, smart TORs that implement one or more functions performed byan NVD, and other mechanisms) to create layers of network abstractionthat can be run on top of the physical network. Virtual networks cantake on many forms, including peer-to-peer networks, IP networks, andothers. Virtual networks are typically either Layer-3 IP networks orLayer-2 VLANs. This method of virtual or overlay networking is oftenreferred to as virtual or overlay Layer-3 networking. Examples ofprotocols developed for virtual networks include IP-in-IP (or GenericRouting Encapsulation (GRE)), Virtual Extensible LAN (VXLAN—IETF RFC7348), Virtual Private Networks (VPNs) (e.g., MPLS Layer-3 VirtualPrivate Networks (RFC 4364)), VMware's NSX, GENEVE (Generic NetworkVirtualization Encapsulation), and others.

For IaaS, the infrastructure (CSPI) provided by a CSP can be configuredto provide virtualized computing resources over a public network (e.g.,the Internet). In an IaaS model, a cloud computing services provider canhost the infrastructure components (e.g., servers, storage devices,network nodes (e.g., hardware), deployment software, platformvirtualization (e.g., a hypervisor layer), or the like). In some cases,an IaaS provider may also supply a variety of services to accompanythose infrastructure components (e.g., billing, monitoring, logging,security, load balancing and clustering, etc.). Thus, as these servicesmay be policy-driven, IaaS users may be able to implement policies todrive load balancing to maintain application availability andperformance. CSPI provides infrastructure and a set of complementarycloud services that enable customers to build and run a wide range ofapplications and services in a highly available hosted distributedenvironment. CSPI offers high-performance compute resources andcapabilities and storage capacity in a flexible virtual network that issecurely accessible from various networked locations such as from acustomer's on-premises network. When a customer subscribes to orregisters for an IaaS service provided by a CSP, the tenancy created forthat customer is a secure and isolated partition within the CSPI wherethe customer can create, organize, and administer their cloud resources.

Customers can build their own virtual networks using compute, memory,and networking resources provided by CSPI. One or more customerresources or workloads, such as compute instances, can be deployed onthese virtual networks. For example, a customer can use resourcesprovided by CSPI to build one or multiple customizable and privatevirtual network(s) referred to as virtual cloud networks (VCNs). Acustomer can deploy one or more customer resources, such as computeinstances, on a customer VCN. Compute instances can take the form ofvirtual machines, bare metal instances, and the like. The CSPI thusprovides infrastructure and a set of complementary cloud services thatenable customers to build and run a wide range of applications andservices in a highly available virtual hosted environment. The customerdoes not manage or control the underlying physical resources provided byCSPI but has control over operating systems, storage, and deployedapplications; and possibly limited control of select networkingcomponents (e.g., firewalls).

The CSP may provide a console that enables customers and networkadministrators to configure, access, and manage resources deployed inthe cloud using CSPI resources. In certain embodiments, the consoleprovides a web-based user interface that can be used to access andmanage CSPI. In some implementations, the console is a web-basedapplication provided by the CSP.

CSPI may support single-tenancy or multi-tenancy architectures. In asingle tenancy architecture, a software (e.g., an application, adatabase) or a hardware component (e.g., a host machine or a server)serves a single customer or tenant. In a multi-tenancy architecture, asoftware or a hardware component serves multiple customers or tenants.Thus, in a multi-tenancy architecture, CSPI resources are shared betweenmultiple customers or tenants. In a multi-tenancy situation, precautionsare taken and safeguards put in place within CSPI to ensure that eachtenant's data is isolated and remains invisible to other tenants.

In a physical network, a network endpoint (“endpoint”) refers to acomputing device or system that is connected to a physical network andcommunicates back and forth with the network to which it is connected. Anetwork endpoint in the physical network may be connected to a LocalArea Network (LAN), a Wide Area Network (WAN), or other type of physicalnetwork. Examples of traditional endpoints in a physical network includemodems, hubs, bridges, switches, routers, and other networking devices,physical computers (or host machines), and the like. Each physicaldevice in the physical network has a fixed network address that can beused to communicate with the device. This fixed network address can be aLayer-2 address (e.g., a MAC address), a fixed Layer-3 address (e.g., anIP address), and the like. In a virtualized environment or in a virtualnetwork, the endpoints can include various virtual endpoints such asvirtual machines that are hosted by components of the physical network(e.g., hosted by physical host machines). These endpoints in the virtualnetwork are addressed by overlay addresses such as overlay Layer-2addresses (e.g., overlay MAC addresses) and overlay Layer-3 addresses(e.g., overlay IP addresses). Network overlays enable flexibility byallowing network managers to move around the overlay addressesassociated with network endpoints using software management (e.g., viasoftware implementing a control plane for the virtual network).Accordingly, unlike in a physical network, in a virtual network, anoverlay address (e.g., an overlay IP address) can be moved from oneendpoint to another using network management software. Since the virtualnetwork is built on top of a physical network, communications betweencomponents in the virtual network involves both the virtual network andthe underlying physical network. In order to facilitate suchcommunications, the components of CSPI are configured to learn and storemappings that map overlay addresses in the virtual network to actualphysical addresses in the substrate network, and vice versa. Thesemappings are then used to facilitate the communications. Customertraffic is encapsulated to facilitate routing in the virtual network.

Accordingly, physical addresses (e.g., physical IP addresses) areassociated with components in physical networks and overlay addresses(e.g., overlay IP addresses) are associated with entities in virtualnetworks. Both the physical IP addresses and overlay IP addresses aretypes of real IP addresses. These are separate from virtual IPaddresses, where a virtual IP address maps to multiple real IPaddresses. A virtual IP address provides a 1-to-many mapping between thevirtual IP address and multiple real IP addresses.

The cloud infrastructure or CSPI is physically hosted in one or moredata centers in one or more regions around the world. The CSPI mayinclude components in the physical or substrate network and virtualizedcomponents (e.g., virtual networks, compute instances, virtual machines,etc.) that are in an virtual network built on top of the physicalnetwork components. In certain embodiments, the CSPI is organized andhosted in realms, regions and availability domains. A region istypically a localized geographic area that contains one or more datacenters. Regions are generally independent of each other and can beseparated by vast distances, for example, across countries or evencontinents. For example, a first region may be in Australia, another onein Japan, yet another one in India, and the like. CSPI resources aredivided among regions such that each region has its own independentsubset of CSPI resources. Each region may provide a set of coreinfrastructure services and resources, such as, compute resources (e.g.,bare metal servers, virtual machine, containers and relatedinfrastructure, etc.); storage resources (e.g., block volume storage,file storage, object storage, archive storage); networking resources(e.g., virtual cloud networks (VCNs), load balancing resources,connections to on-premise networks), database resources; edge networkingresources (e.g., DNS); and access management and monitoring resources,and others. Each region generally has multiple paths connecting it toother regions in the realm.

Generally, an application is deployed in a region (i.e., deployed oninfrastructure associated with that region) where it is most heavilyused, because using nearby resources is faster than using distantresources. Applications can also be deployed in different regions forvarious reasons, such as redundancy to mitigate the risk of region-wideevents such as large weather systems or earthquakes, to meet varyingrequirements for legal jurisdictions, tax domains, and other business orsocial criteria, and the like.

The data centers within a region can be further organized and subdividedinto availability domains (ADs). An availability domain may correspondto one or more data centers located within a region. A region can becomposed of one or more availability domains. In such a distributedenvironment, CSPI resources are either region-specific, such as avirtual cloud network (VCN), or availability domain-specific, such as acompute instance.

ADs within a region are isolated from each other, fault tolerant, andare configured such that they are very unlikely to fail simultaneously.This is achieved by the ADs not sharing critical infrastructureresources such as networking, physical cables, cable paths, cable entrypoints, etc., such that a failure at one AD within a region is unlikelyto impact the availability of the other ADs within the same region. TheADs within the same region may be connected to each other by a lowlatency, high bandwidth network, which makes it possible to providehigh-availability connectivity to other networks (e.g., the Internet,customers' on-premise networks, etc.) and to build replicated systems inmultiple ADs for both high-availability and disaster recovery. Cloudservices use multiple ADs to ensure high availability and to protectagainst resource failure. As the infrastructure provided by the IaaSprovider grows, more regions and ADs may be added with additionalcapacity. Traffic between availability domains is usually encrypted.

In certain embodiments, regions are grouped into realms. A realm is alogical collection of regions. Realms are isolated from each other anddo not share any data. Regions in the same realm may communicate witheach other, but regions in different realms cannot. A customer's tenancyor account with the CSP exists in a single realm and can be spreadacross one or more regions that belong to that realm. Typically, when acustomer subscribes to an IaaS service, a tenancy or account is createdfor that customer in the customer-specified region (referred to as the“home” region) within a realm. A customer can extend the customer'stenancy across one or more other regions within the realm. A customercannot access regions that are not in the realm where the customer'stenancy exists.

An IaaS provider can provide multiple realms, each realm catered to aparticular set of customers or users. For example, a commercial realmmay be provided for commercial customers. As another example, a realmmay be provided for a specific country for customers within thatcountry. As yet another example, a government realm may be provided fora government, and the like. For example, the government realm may becatered for a specific government and may have a heightened level ofsecurity than a commercial realm. For example, Oracle CloudInfrastructure (OCI) currently offers a realm for commercial regions andtwo realms (e.g., FedRAMP authorized and IL5 authorized) for governmentcloud regions.

In certain embodiments, an AD can be subdivided into one or more faultdomains. A fault domain is a grouping of infrastructure resources withinan AD to provide anti-affinity. Fault domains allow for the distributionof compute instances such that the instances are not on the samephysical hardware within a single AD. This is known as anti-affinity. Afault domain refers to a set of hardware components (computers,switches, and more) that share a single point of failure. A compute poolis logically divided up into fault domains. Due to this, a hardwarefailure or compute hardware maintenance event that affects one faultdomain does not affect instances in other fault domains. Depending onthe embodiment, the number of fault domains for each AD may vary. Forinstance, in certain embodiments each AD contains three fault domains. Afault domain acts as a logical data center within an AD.

When a customer subscribes to an IaaS service, resources from CSPI areprovisioned for the customer and associated with the customer's tenancy.The customer can use these provisioned resources to build privatenetworks and deploy resources on these networks. The customer networksthat are hosted in the cloud by the CSPI are referred to as virtualcloud networks (VCNs). A customer can set up one or more virtual cloudnetworks (VCNs) using CSPI resources allocated for the customer. A VCNis a virtual or software defined private network. The customer resourcesthat are deployed in the customer's VCN can include compute instances(e.g., virtual machines, bare-metal instances) and other resources.These compute instances may represent various customer workloads such asapplications, load balancers, databases, and the like. A computeinstance deployed on a VCN can communicate with public accessibleendpoints (“public endpoints”) over a public network such as theInternet, with other instances in the same VCN or other VCNs (e.g., thecustomer's other VCNs, or VCNs not belonging to the customer), with thecustomer's on-premise data centers or networks, and with serviceendpoints, and other types of endpoints.

The CSP may provide various services using the CSPI. In some instances,customers of CSPI may themselves act like service providers and provideservices using CSPI resources. A service provider may expose a serviceendpoint, which is characterized by identification information (e.g., anIP Address, a DNS name and port). A customer's resource (e.g., a computeinstance) can consume a particular service by accessing a serviceendpoint exposed by the service for that particular service. Theseservice endpoints are generally endpoints that are publicly accessibleby users using public IP addresses associated with the endpoints via apublic communication network such as the Internet. Network endpointsthat are publicly accessible are also sometimes referred to as publicendpoints.

In certain embodiments, a service provider may expose a service via anendpoint (sometimes referred to as a service endpoint) for the service.Customers of the service can then use this service endpoint to accessthe service. In certain implementations, a service endpoint provided fora service can be accessed by multiple customers that intend to consumethat service. In other implementations, a dedicated service endpoint maybe provided for a customer such that only that customer can access theservice using that dedicated service endpoint.

In certain embodiments, when a VCN is created, it is associated with aprivate overlay Classless Inter-Domain Routing (CIDR) address space,which is a range of private overlay IP addresses that are assigned tothe VCN (e.g., 10.0/16). A VCN includes associated subnets, routetables, and gateways. A VCN resides within a single region but can spanone or more or all of the region's availability domains. A gateway is avirtual interface that is configured for a VCN and enables communicationof traffic to and from the VCN to one or more endpoints outside the VCN.One or more different types of gateways may be configured for a VCN toenable communication to and from different types of endpoints.

A VCN can be subdivided into one or more sub-networks such as one ormore subnets. A subnet is thus a unit of configuration or a subdivisionthat can be created within a VCN. A VCN can have one or multiplesubnets. Each subnet within a VCN is associated with a contiguous rangeof overlay IP addresses (e.g., 10.0.0.0/24 and 10.0.1.0/24) that do notoverlap with other subnets in that VCN and which represent an addressspace subset within the address space of the VCN.

Each compute instance is associated with a virtual network interfacecard (VNIC), that enables the compute instance to participate in asubnet of a VCN. A VNIC is a logical representation of physical NetworkInterface Card (NIC). In general. a VNIC is an interface between anentity (e.g., a compute instance, a service) and a virtual network. AVNIC exists in a subnet, has one or more associated IP addresses, andassociated security rules or policies. A VNIC is equivalent to a Layer-2port on a switch. A VNIC is attached to a compute instance and to asubnet within a VCN. A VNIC associated with a compute instance enablesthe compute instance to be a part of a subnet of a VCN and enables thecompute instance to communicate (e.g., send and receive packets) withendpoints that are on the same subnet as the compute instance, withendpoints in different subnets in the VCN, or with endpoints outside theVCN. The VNIC associated with a compute instance thus determines how thecompute instance connects with endpoints inside and outside the VCN. AVNIC for a compute instance is created and associated with that computeinstance when the compute instance is created and added to a subnetwithin a VCN. For a subnet comprising a set of compute instances, thesubnet contains the VNICs corresponding to the set of compute instances,each VNIC attached to a compute instance within the set of computerinstances.

Each compute instance is assigned a private overlay IP address via theVNIC associated with the compute instance. This private overlay IPaddress is assigned to the VNIC that is associated with the computeinstance when the compute instance is created and used for routingtraffic to and from the compute instance. All VNICs in a given subnetuse the same route table, security lists, and DHCP options. As describedabove, each subnet within a VCN is associated with a contiguous range ofoverlay IP addresses (e.g., 10.0.0.0/24 and 10.0.1.0/24) that do notoverlap with other subnets in that VCN and which represent an addressspace subset within the address space of the VCN. For a VNIC on aparticular subnet of a VCN, the private overlay IP address that isassigned to the VNIC is an address from the contiguous range of overlayIP addresses allocated for the subnet.

In certain embodiments, a compute instance may optionally be assignedadditional overlay IP addresses in addition to the private overlay IPaddress, such as, for example, one or more public IP addresses if in apublic subnet. These multiple addresses are assigned either on the sameVNIC or over multiple VNICs that are associated with the computeinstance. Each instance however has a primary VNIC that is createdduring instance launch and is associated with the overlay private IPaddress assigned to the instance—this primary VNIC cannot be removed.Additional VNICs, referred to as secondary VNICs, can be added to anexisting instance in the same availability domain as the primary VNIC.All the VNICs are in the same availability domain as the instance. Asecondary VNIC can be in a subnet in the same VCN as the primary VNIC,or in a different subnet that is either in the same VCN or a differentone.

A compute instance may optionally be assigned a public IP address if itis in a public subnet. A subnet can be designated as either a publicsubnet or a private subnet at the time the subnet is created. A privatesubnet means that the resources (e.g., compute instances) and associatedVNICs in the subnet cannot have public overlay IP addresses. A publicsubnet means that the resources and associated VNICs in the subnet canhave public IP addresses. A customer can designate a subnet to existeither in a single availability domain or across multiple availabilitydomains in a region or realm.

As described above, a VCN may be subdivided into one or more subnets. Incertain embodiments, a Virtual Router (VR) configured for the VCN(referred to as the VCN VR or just VR) enables communications betweenthe subnets of the VCN. For a subnet within a VCN, the VR represents alogical gateway for that subnet that enables the subnet (i.e., thecompute instances on that subnet) to communicate with endpoints on othersubnets within the VCN, and with other endpoints outside the VCN. TheVCN VR is a logical entity that is configured to route traffic betweenVNICs in the VCN and virtual gateways (“gateways”) associated with theVCN. Gateways are further described below with respect to FIG. 1 . A VCNVR is a Layer-3/IP Layer concept. In one embodiment, there is one VCN VRfor a VCN where the VCN VR has potentially an unlimited number of portsaddressed by IP addresses, with one port for each subnet of the VCN. Inthis manner, the VCN VR has a different IP address for each subnet inthe VCN that the VCN VR is attached to. The VR is also connected to thevarious gateways configured for a VCN. In certain embodiments, aparticular overlay IP address from the overlay IP address range for asubnet is reserved for a port of the VCN VR for that subnet. Forexample, consider a VCN having two subnets with associated addressranges 10.0/16 and 10.1/16, respectively. For the first subnet withinthe VCN with address range 10.0/16, an address from this range isreserved for a port of the VCN VR for that subnet. In some instances,the first IP address from the range may be reserved for the VCN VR. Forexample, for the subnet with overlay IP address range 10.0/16, IPaddress 10.0.0.1 may be reserved for a port of the VCN VR for thatsubnet. For the second subnet within the same VCN with address range10.1/16, the VCN VR may have a port for that second subnet with IPaddress 10.1.0.1. The VCN VR has a different IP address for each of thesubnets in the VCN.

In some other embodiments, each subnet within a VCN may have its ownassociated VR that is addressable by the subnet using a reserved ordefault IP address associated with the VR. The reserved or default IPaddress may, for example, be the first IP address from the range of IPaddresses associated with that subnet. The VNICs in the subnet cancommunicate (e.g., send and receive packets) with the VR associated withthe subnet using this default or reserved IP address. In such anembodiment, the VR is the ingress/egress point for that subnet. The VRassociated with a subnet within the VCN can communicate with other VRsassociated with other subnets within the VCN. The VRs can alsocommunicate with gateways associated with the VCN. The VR function for asubnet is running on or executed by one or more NVDs executing VNICsfunctionality for VNICs in the subnet.

Route tables, security rules, and DHCP options may be configured for aVCN. Route tables are virtual route tables for the VCN and include rulesto route traffic from subnets within the VCN to destinations outside theVCN by way of gateways or specially configured instances. A VCN's routetables can be customized to control how packets are forwarded/routed toand from the VCN. DHCP options refers to configuration information thatis automatically provided to the instances when they boot up.

Security rules configured for a VCN represent overlay firewall rules forthe VCN. The security rules can include ingress and egress rules, andspecify the types of traffic (e.g., based upon protocol and port) thatis allowed in and out of the instances within the VCN. The customer canchoose whether a given rule is stateful or stateless. For instance, thecustomer can allow incoming SSH traffic from anywhere to a set ofinstances by setting up a stateful ingress rule with source CIDR0.0.0.0/0, and destination TCP port 22. Security rules can beimplemented using network security groups or security lists. A networksecurity group consists of a set of security rules that apply only tothe resources in that group. A security list, on the other hand,includes rules that apply to all the resources in any subnet that usesthe security list. A VCN may be provided with a default security listwith default security rules. DHCP options configured for a VCN provideconfiguration information that is automatically provided to theinstances in the VCN when the instances boot up.

In certain embodiments, the configuration information for a VCN isdetermined and stored by a VCN Control Plane. The configurationinformation for a VCN may include, for example, information about: theaddress range associated with the VCN, subnets within the VCN andassociated information, one or more VRs associated with the VCN, computeinstances in the VCN and associated VNICs, NVDs executing the variousvirtualization network functions (e.g., VNICs, VRs, gateways) associatedwith the VCN, state information for the VCN, and other VCN-relatedinformation. In certain embodiments, a VCN Distribution Servicepublishes the configuration information stored by the VCN Control Plane,or portions thereof, to the NVDs. The distributed information may beused to update information (e.g., forwarding tables, routing tables,etc.) stored and used by the NVDs to forward packets to and from thecompute instances in the VCN.

In certain embodiments, the creation of VCNs and subnets are handled bya VCN Control Plane (CP) and the launching of compute instances ishandled by a Compute Control Plane. The Compute Control Plane isresponsible for allocating the physical resources for the computeinstance and then calls the VCN Control Plane to create and attach VNICsto the compute instance. The VCN CP also sends VCN data mappings to theVCN data plane that is configured to perform packet forwarding androuting functions. In certain embodiments, the VCN CP provides adistribution service that is responsible for providing updates to theVCN data plane. Examples of a VCN Control Plane are also depicted inFIGS. 16, 17, 18, and 19 (see references 1616, 1716, 1816, and 1916) anddescribed below.

A customer may create one or more VCNs using resources hosted by CSPI. Acompute instance deployed on a customer VCN may communicate withdifferent endpoints. These endpoints can include endpoints that arehosted by CSPI and endpoints outside CSPI.

Various different architectures for implementing cloud-based serviceusing CSPI are depicted in FIGS. 1, 2, 3, 4, 5, 16, 17, 18, and 20 , andare described below. FIG. 1 is a high level diagram of a distributedenvironment 100 showing an overlay or customer VCN hosted by CSPIaccording to certain embodiments. The distributed environment depictedin FIG. 1 includes multiple components in the overlay network.Distributed environment 100 depicted in FIG. 1 is merely an example andis not intended to unduly limit the scope of claimed embodiments. Manyvariations, alternatives, and modifications are possible. For example,in some implementations, the distributed environment depicted in FIG. 1may have more or fewer systems or components than those shown in FIG. 1, may combine two or more systems, or may have a different configurationor arrangement of systems.

As shown in the example depicted in FIG. 1 , distributed environment 100comprises CSPI 101 that provides services and resources that customerscan subscribe to and use to build their virtual cloud networks (VCNs).In certain embodiments, CSPI 101 offers IaaS services to subscribingcustomers. The data centers within CSPI 101 may be organized into one ormore regions. One example region “Region US” 102 is shown in FIG. 1 . Acustomer has configured a customer VCN 104 for region 102. The customermay deploy various compute instances on VCN 104, where the computeinstances may include virtual machines or bare metal instances. Examplesof instances include applications, database, load balancers, and thelike.

In the embodiment depicted in FIG. 1 , customer VCN 104 comprises twosubnets, namely, “Subnet-1” and “Subnet-2”, each subnet with its ownCIDR IP address range. In FIG. 1 , the overlay IP address range forSubnet-1 is 10.0/16 and the address range for Subnet-2 is 10.1/16. A VCNVirtual Router 105 represents a logical gateway for the VCN that enablescommunications between subnets of the VCN 104, and with other endpointsoutside the VCN. VCN VR 105 is configured to route traffic between VNICsin VCN 104 and gateways associated with VCN 104. VCN VR 105 provides aport for each subnet of VCN 104. For example, VR 105 may provide a portwith IP address 10.0.0.1 for Subnet-1 and a port with IP address10.1.0.1 for Subnet-2.

Multiple compute instances may be deployed on each subnet, where thecompute instances can be virtual machine instances, and/or bare metalinstances. The compute instances in a subnet may be hosted by one ormore host machines within CSPI 101. A compute instance participates in asubnet via a VNIC associated with the compute instance. For example, asshown in FIG. 1 , a compute instance C1 is part of Subnet-1 via a VNICassociated with the compute instance. Likewise, compute instance C2 ispart of Subnet-1 via a VNIC associated with C2. In a similar manner,multiple compute instances, which may be virtual machine instances orbare metal instances, may be part of Subnet-1. Via its associated VNIC,each compute instance is assigned a private overlay IP address and a MACaddress. For example, in FIG. 1 , compute instance C1 has an overlay IPaddress of 10.0.0.2 and a MAC address of M1, while compute instance C2has an private overlay IP address of 10.0.0.3 and a MAC address of M2.Each compute instance in Subnet-1, including compute instances C1 andC2, has a default route to VCN VR 105 using IP address 10.0.0.1, whichis the IP address for a port of VCN VR 105 for Subnet-1.

Subnet-2 can have multiple compute instances deployed on it, includingvirtual machine instances and/or bare metal instances. For example, asshown in FIG. 1 , compute instances D1 and D2 are part of Subnet-2 viaVNICs associated with the respective compute instances. In theembodiment depicted in FIG. 1 , compute instance D1 has an overlay IPaddress of 10.1.0.2 and a MAC address of MM1, while compute instance D2has an private overlay IP address of 10.1.0.3 and a MAC address of MM2.Each compute instance in Subnet-2, including compute instances D1 andD2, has a default route to VCN VR 105 using IP address 10.1.0.1, whichis the IP address for a port of VCN VR 105 for Subnet-2.

VCN A 104 may also include one or more load balancers. For example, aload balancer may be provided for a subnet and may be configured to loadbalance traffic across multiple compute instances on the subnet. A loadbalancer may also be provided to load balance traffic across subnets inthe VCN.

A particular compute instance deployed on VCN 104 can communicate withvarious different endpoints. These endpoints may include endpoints thatare hosted by CSPI 200 and endpoints outside CSPI 200. Endpoints thatare hosted by CSPI 101 may include: an endpoint on the same subnet asthe particular compute instance (e.g., communications between twocompute instances in Subnet-1); an endpoint on a different subnet butwithin the same VCN (e.g., communication between a compute instance inSubnet-1 and a compute instance in Subnet-2); an endpoint in a differentVCN in the same region (e.g., communications between a compute instancein Subnet-1 and an endpoint in a VCN in the same region 106 or 110,communications between a compute instance in Subnet-1 and an endpoint inservice network 110 in the same region); or an endpoint in a VCN in adifferent region (e.g., communications between a compute instance inSubnet-1 and an endpoint in a VCN in a different region 108). A computeinstance in a subnet hosted by CSPI 101 may also communicate withendpoints that are not hosted by CSPI 101 (i.e., are outside CSPI 101).These outside endpoints include endpoints in the customer's on-premisenetwork 116, endpoints within other remote cloud hosted networks 118,public endpoints 114 accessible via a public network such as theInternet, and other endpoints.

Communications between compute instances on the same subnet arefacilitated using VNICs associated with the source compute instance andthe destination compute instance. For example, compute instance C1 inSubnet-1 may want to send packets to compute instance C2 in Subnet-1.For a packet originating at a source compute instance and whosedestination is another compute instance in the same subnet, the packetis first processed by the VNIC associated with the source computeinstance. Processing performed by the VNIC associated with the sourcecompute instance can include determining destination information for thepacket from the packet headers, identifying any policies (e.g., securitylists) configured for the VNIC associated with the source computeinstance, determining a next hop for the packet, performing any packetencapsulation/decapsulation functions as needed, and thenforwarding/routing the packet to the next hop with the goal offacilitating communication of the packet to its intended destination.When the destination compute instance is in the same subnet as thesource compute instance, the VNIC associated with the source computeinstance is configured to identify the VNIC associated with thedestination compute instance and forward the packet to that VNIC forprocessing. The VNIC associated with the destination compute instance isthen executed and forwards the packet to the destination computeinstance.

For a packet to be communicated from a compute instance in a subnet toan endpoint in a different subnet in the same VCN, the communication isfacilitated by the VNICs associated with the source and destinationcompute instances and the VCN VR. For example, if compute instance C1 inSubnet-1 in FIG. 1 wants to send a packet to compute instance D1 inSubnet-2, the packet is first processed by the VNIC associated withcompute instance C1. The VNIC associated with compute instance C1 isconfigured to route the packet to the VCN VR 105 using default route orport 10.0.0.1 of the VCN VR. VCN VR 105 is configured to route thepacket to Subnet-2 using port 10.1.0.1. The packet is then received andprocessed by the VNIC associated with D1 and the VNIC forwards thepacket to compute instance D1.

For a packet to be communicated from a compute instance in VCN 104 to anendpoint that is outside VCN 104, the communication is facilitated bythe VNIC associated with the source compute instance, VCN VR 105, andgateways associated with VCN 104. One or more types of gateways may beassociated with VCN 104. A gateway is an interface between a VCN andanother endpoint, where the another endpoint is outside the VCN. Agateway is a Layer-3/IP layer concept and enables a VCN to communicatewith endpoints outside the VCN. A gateway thus facilitates traffic flowbetween a VCN and other VCNs or networks. Various different types ofgateways may be configured for a VCN to facilitate different types ofcommunications with different types of endpoints. Depending upon thegateway, the communications may be over public networks (e.g., theInternet) or over private networks. Various communication protocols maybe used for these communications.

For example, compute instance C1 may want to communicate with anendpoint outside VCN 104. The packet may be first processed by the VNICassociated with source compute instance C1. The VNIC processingdetermines that the destination for the packet is outside the Subnet-1of C1. The VNIC associated with C1 may forward the packet to VCN VR 105for VCN 104. VCN VR 105 then processes the packet and as part of theprocessing, based upon the destination for the packet, determines aparticular gateway associated with VCN 104 as the next hop for thepacket. VCN VR 105 may then forward the packet to the particularidentified gateway. For example, if the destination is an endpointwithin the customer's on-premise network, then the packet may beforwarded by VCN VR 105 to Dynamic Routing Gateway (DRG) gateway 122configured for VCN 104. The packet may then be forwarded from thegateway to a next hop to facilitate communication of the packet to itfinal intended destination.

Various different types of gateways may be configured for a VCN.Examples of gateways that may be configured for a VCN are depicted inFIG. 1 and described below. Examples of gateways associated with a VCNare also depicted in FIGS. 16, 17, 18, and 19 (for example, gatewaysreferenced by reference numbers 1634, 1636, 1638, 1734, 1736, 1738,1834, 1836, 1838, 1934, 1936, and 1938) and described below. As shown inthe embodiment depicted in FIG. 1 , a Dynamic Routing Gateway (DRG) 122may be added to or be associated with customer VCN 104 and provides apath for private network traffic communication between customer VCN 104and another endpoint, where the another endpoint can be the customer'son-premise network 116, a VCN 108 in a different region of CSPI 101, orother remote cloud networks 118 not hosted by CSPI 101. Customeron-premise network 116 may be a customer network or a customer datacenter built using the customer's resources. Access to customeron-premise network 116 is generally very restricted. For a customer thathas both a customer on-premise network 116 and one or more VCNs 104deployed or hosted in the cloud by CSPI 101, the customer may want theiron-premise network 116 and their cloud-based VCN 104 to be able tocommunicate with each other. This enables a customer to build anextended hybrid environment encompassing the customer's VCN 104 hostedby CSPI 101 and their on-premises network 116. DRG 122 enables thiscommunication. To enable such communications, a communication channel124 is set up where one endpoint of the channel is in customeron-premise network 116 and the other endpoint is in CSPI 101 andconnected to customer VCN 104. Communication channel 124 can be overpublic communication networks such as the Internet or privatecommunication networks. Various different communication protocols may beused such as IPsec VPN technology over a public communication networksuch as the Internet, Oracle's FastConnect technology that uses aprivate network instead of a public network, and others. The device orequipment in customer on-premise network 116 that forms one end pointfor communication channel 124 is referred to as the customer premiseequipment (CPE), such as CPE 126 depicted in FIG. 1 . On the CSPI 101side, the endpoint may be a host machine executing DRG 122.

In certain embodiments, a Remote Peering Connection (RPC) can be addedto a DRG, which allows a customer to peer one VCN with another VCN in adifferent region. Using such an RPC, customer VCN 104 can use DRG 122 toconnect with a VCN 108 in another region. DRG 122 may also be used tocommunicate with other remote cloud networks 118, not hosted by CSPI 101such as a Microsoft Azure cloud, Amazon AWS cloud, and others.

As shown in FIG. 1 , an Internet Gateway (IGW) 120 may be configured forcustomer VCN 104 the enables a compute instance on VCN 104 tocommunicate with public endpoints 114 accessible over a public networksuch as the Internet. IGW 120 is a gateway that connects a VCN to apublic network such as the Internet. IGW 120 enables a public subnet(where the resources in the public subnet have public overlay IPaddresses) within a VCN, such as VCN 104, direct access to publicendpoints 112 on a public network 114 such as the Internet. Using IGW120, connections can be initiated from a subnet within VCN 104 or fromthe Internet.

A Network Address Translation (NAT) gateway 128 can be configured forcustomer's VCN 104 and enables cloud resources in the customer's VCN,which do not have dedicated public overlay IP addresses, access to theInternet and it does so without exposing those resources to directincoming Internet connections (e.g., L4-L7 connections). This enables aprivate subnet within a VCN, such as private Subnet-1 in VCN 104, withprivate access to public endpoints on the Internet. In NAT gateways,connections can be initiated only from the private subnet to the publicInternet and not from the Internet to the private subnet.

In certain embodiments, a Service Gateway (SGW) 126 can be configuredfor customer VCN 104 and provides a path for private network trafficbetween VCN 104 and supported services endpoints in a service network110. In certain embodiments, service network 110 may be provided by theCSP and may provide various services. An example of such a servicenetwork is Oracle's Services Network, which provides various servicesthat can be used by customers. For example, a compute instance (e.g., adatabase system) in a private subnet of customer VCN 104 can back updata to a service endpoint (e.g., Object Storage) without needing publicIP addresses or access to the Internet. In certain embodiments, a VCNcan have only one SGW, and connections can only be initiated from asubnet within the VCN and not from service network 110. If a VCN ispeered with another, resources in the other VCN typically cannot accessthe SGW. Resources in on-premises networks that are connected to a VCNwith FastConnect or VPN Connect can also use the service gatewayconfigured for that VCN.

In certain implementations, SGW 126 uses the concept of a serviceClassless Inter-Domain Routing (CIDR) label, which is a string thatrepresents all the regional public IP address ranges for the service orgroup of services of interest. The customer uses the service CIDR labelwhen they configure the SGW and related route rules to control trafficto the service. The customer can optionally utilize it when configuringsecurity rules without needing to adjust them if the service's public IPaddresses change in the future.

A Local Peering Gateway (LPG) 132 is a gateway that can be added tocustomer VCN 104 and enables VCN 104 to peer with another VCN in thesame region. Peering means that the VCNs communicate using private IPaddresses, without the traffic traversing a public network such as theInternet or without routing the traffic through the customer'son-premises network 116. In preferred embodiments, a VCN has a separateLPG for each peering it establishes. Local Peering or VCN Peering is acommon practice used to establish network connectivity between differentapplications or infrastructure management functions.

Service providers, such as providers of services in service network 110,may provide access to services using different access models. Accordingto a public access model, services may be exposed as public endpointsthat are publicly accessible by compute instance in a customer VCN via apublic network such as the Internet and or may be privately accessiblevia SGW 126. According to a specific private access model, services aremade accessible as private IP endpoints in a private subnet in thecustomer's VCN. This is referred to as a Private Endpoint (PE) accessand enables a service provider to expose their service as an instance inthe customer's private network. A Private Endpoint resource represents aservice within the customer's VCN. Each PE manifests as a VNIC (referredto as a PE-VNIC, with one or more private IPs) in a subnet chosen by thecustomer in the customer's VCN. APE thus provides a way to present aservice within a private customer VCN subnet using a VNIC. Since theendpoint is exposed as a VNIC, all the features associates with a VNICsuch as routing rules, security lists, etc., are now available for thePE VNIC.

A service provider can register their service to enable access through aPE. The provider can associate policies with the service that restrictsthe service's visibility to the customer tenancies. A provider canregister multiple services under a single virtual IP address (VIP),especially for multi-tenant services. There may be multiple such privateendpoints (in multiple VCNs) that represent the same service.

Compute instances in the private subnet can then use the PE VNIC'sprivate IP address or the service DNS name to access the service.Compute instances in the customer VCN can access the service by sendingtraffic to the private IP address of the PE in the customer VCN. APrivate Access Gateway (PAGW) 130 is a gateway resource that can beattached to a service provider VCN (e.g., a VCN in service network 110)that acts as an ingress/egress point for all traffic from/to customersubnet private endpoints. PAGW 130 enables a provider to scale thenumber of PE connections without utilizing its internal IP addressresources. A provider needs only configure one PAGW for any number ofservices registered in a single VCN. Providers can represent a serviceas a private endpoint in multiple VCNs of one or more customers. Fromthe customer's perspective, the PE VNIC, which, instead of beingattached to a customer's instance, appears attached to the service withwhich the customer wishes to interact. The traffic destined to theprivate endpoint is routed via PAGW 130 to the service. These arereferred to as customer-to-service private connections (C2Sconnections).

The PE concept can also be used to extend the private access for theservice to customer's on-premises networks and data centers, by allowingthe traffic to flow through FastConnect/IPsec links and the privateendpoint in the customer VCN. Private access for the service can also beextended to the customer's peered VCNs, by allowing the traffic to flowbetween LPG 132 and the PE in the customer's VCN.

A customer can control routing in a VCN at the subnet level, so thecustomer can specify which subnets in the customer's VCN, such as VCN104, use each gateway. A VCN's route tables are used to decide iftraffic is allowed out of a VCN through a particular gateway. Forexample, in a particular instance, a route table for a public subnetwithin customer VCN 104 may send non-local traffic through IGW 120. Theroute table for a private subnet within the same customer VCN 104 maysend traffic destined for CSP services through SGW 126. All remainingtraffic may be sent via the NAT gateway 128. Route tables only controltraffic going out of a VCN.

Security lists associated with a VCN are used to control traffic thatcomes into a VCN via a gateway via inbound connections. All resources ina subnet use the same route table and security lists. Security lists maybe used to control specific types of traffic allowed in and out ofinstances in a subnet of a VCN. Security list rules may comprise ingress(inbound) and egress (outbound) rules. For example, an ingress rule mayspecify an allowed source address range, while an egress rule mayspecify an allowed destination address range. Security rules may specifya particular protocol (e.g., TCP, ICMP), a particular port (e.g., 22 forSSH, 3389 for Windows RDP), etc. In certain implementations, aninstance's operating system may enforce its own firewall rules that arealigned with the security list rules. Rules may be stateful (e.g., aconnection is tracked and the response is automatically allowed withoutan explicit security list rule for the response traffic) or stateless.

Access from a customer VCN (i.e., by a resource or compute instancedeployed on VCN 104) can be categorized as public access, privateaccess, or dedicated access. Public access refers to an access modelwhere a public IP address or a NAT is used to access a public endpoint.Private access enables customer workloads in VCN 104 with private IPaddresses (e.g., resources in a private subnet) to access serviceswithout traversing a public network such as the Internet. In certainembodiments, CSPI 101 enables customer VCN workloads with private IPaddresses to access the (public service endpoints of) services using aservice gateway. A service gateway thus offers a private access model byestablishing a virtual link between the customer's VCN and the service'spublic endpoint residing outside the customer's private network.

Additionally, CSPI may offer dedicated public access using technologiessuch as FastConnect public peering where customer on-premises instancescan access one or more services in a customer VCN using a FastConnectconnection and without traversing a public network such as the Internet.CSPI also may also offer dedicated private access using FastConnectprivate peering where customer on-premises instances with private IPaddresses can access the customer's VCN workloads using a FastConnectconnection. FastConnect is a network connectivity alternative to usingthe public Internet to connect a customer's on-premise network to CSPIand its services. FastConnect provides an easy, elastic, and economicalway to create a dedicated and private connection with higher bandwidthoptions and a more reliable and consistent networking experience whencompared to Internet-based connections.

FIG. 1 and the accompanying description above describes variousvirtualized components in an example virtual network. As describedabove, the virtual network is built on the underlying physical orsubstrate network. FIG. 2 depicts a simplified architectural diagram ofthe physical components in the physical network within CSPI 200 thatprovide the underlay for the virtual network according to certainembodiments. As shown, CSPI 200 provides a distributed environmentcomprising components and resources (e.g., compute, memory, andnetworking resources) provided by a cloud service provider (CSP). Thesecomponents and resources are used to provide cloud services (e.g., IaaSservices) to subscribing customers, i.e., customers that have subscribedto one or more services provided by the CSP. Based upon the servicessubscribed to by a customer, a subset of resources (e.g., compute,memory, and networking resources) of CSPI 200 are provisioned for thecustomer. Customers can then build their own cloud-based (i.e.,CSPI-hosted) customizable and private virtual networks using physicalcompute, memory, and networking resources provided by CSPI 200. Aspreviously indicated, these customer networks are referred to as virtualcloud networks (VCNs). A customer can deploy one or more customerresources, such as compute instances, on these customer VCNs. Computeinstances can be in the form of virtual machines, bare metal instances,and the like. CSPI 200 provides infrastructure and a set ofcomplementary cloud services that enable customers to build and run awide range of applications and services in a highly available hostedenvironment.

In the example embodiment depicted in FIG. 2 , the physical componentsof CSPI 200 include one or more physical host machines or physicalservers (e.g., 202, 206, 208), network virtualization devices (NVDs)(e.g., 210, 212), top-of-rack (TOR) switches (e.g., 214, 216), and aphysical network (e.g., 218), and switches in physical network 218. Thephysical host machines or servers may host and execute various computeinstances that participate in one or more subnets of a VCN. The computeinstances may include virtual machine instances, and bare metalinstances. For example, the various compute instances depicted in FIG. 1may be hosted by the physical host machines depicted in FIG. 2 . Thevirtual machine compute instances in a VCN may be executed by one hostmachine or by multiple different host machines. The physical hostmachines may also host virtual host machines, container-based hosts orfunctions, and the like. The VNICs and VCN VR depicted in FIG. 1 may beexecuted by the NVDs depicted in FIG. 2 . The gateways depicted in FIG.1 may be executed by the host machines and/or by the NVDs depicted inFIG. 2 .

The host machines or servers may execute a hypervisor (also referred toas a virtual machine monitor or VMM) that creates and enables avirtualized environment on the host machines. The virtualization orvirtualized environment facilitates cloud-based computing. One or morecompute instances may be created, executed, and managed on a hostmachine by a hypervisor on that host machine. The hypervisor on a hostmachine enables the physical computing resources of the host machine(e.g., compute, memory, and networking resources) to be shared betweenthe various compute instances executed by the host machine.

For example, as depicted in FIG. 2 , host machines 202 and 208 executehypervisors 260 and 266, respectively. These hypervisors may beimplemented using software, firmware, or hardware, or combinationsthereof. Typically, a hypervisor is a process or a software layer thatsits on top of the host machine's operating system (OS), which in turnexecutes on the hardware processors of the host machine. The hypervisorprovides a virtualized environment by enabling the physical computingresources (e.g., processing resources such as processors/cores, memoryresources, networking resources) of the host machine to be shared amongthe various virtual machine compute instances executed by the hostmachine. For example, in FIG. 2 , hypervisor 260 may sit on top of theOS of host machine 202 and enables the computing resources (e.g.,processing, memory, and networking resources) of host machine 202 to beshared between compute instances (e.g., virtual machines) executed byhost machine 202. A virtual machine can have its own operating system(referred to as a guest operating system), which may be the same as ordifferent from the OS of the host machine. The operating system of avirtual machine executed by a host machine may be the same as ordifferent from the operating system of another virtual machine executedby the same host machine. A hypervisor thus enables multiple operatingsystems to be executed alongside each other while sharing the samecomputing resources of the host machine. The host machines depicted inFIG. 2 may have the same or different types of hypervisors.

A compute instance can be a virtual machine instance or a bare metalinstance. In FIG. 2 , compute instances 268 on host machine 202 and 274on host machine 208 are examples of virtual machine instances. Hostmachine 206 is an example of a bare metal instance that is provided to acustomer.

In certain instances, an entire host machine may be provisioned to asingle customer, and all of the one or more compute instances (eithervirtual machines or bare metal instance) hosted by that host machinebelong to that same customer. In other instances, a host machine may beshared between multiple customers (i.e., multiple tenants). In such amulti-tenancy scenario, a host machine may host virtual machine computeinstances belonging to different customers. These compute instances maybe members of different VCNs of different customers. In certainembodiments, a bare metal compute instance is hosted by a bare metalserver without a hypervisor. When a bare metal compute instance isprovisioned, a single customer or tenant maintains control of thephysical CPU, memory, and network interfaces of the host machine hostingthe bare metal instance and the host machine is not shared with othercustomers or tenants.

As previously described, each compute instance that is part of a VCN isassociated with a VNIC that enables the compute instance to become amember of a subnet of the VCN. The VNIC associated with a computeinstance facilitates the communication of packets or frames to and fromthe compute instance. A VNIC is associated with a compute instance whenthe compute instance is created. In certain embodiments, for a computeinstance executed by a host machine, the VNIC associated with thatcompute instance is executed by an NVD connected to the host machine.For example, in FIG. 2 , host machine 202 executes a virtual machinecompute instance 268 that is associated with VNIC 276, and VNIC 276 isexecuted by NVD 210 connected to host machine 202. As another example,bare metal instance 272 hosted by host machine 206 is associated withVNIC 280 that is executed by NVD 212 connected to host machine 206. Asyet another example, VNIC 284 is associated with compute instance 274executed by host machine 208, and VNIC 284 is executed by NVD 212connected to host machine 208.

For compute instances hosted by a host machine, an NVD connected to thathost machine also executes VCN VRs corresponding to VCNs of which thecompute instances are members. For example, in the embodiment depictedin FIG. 2 , NVD 210 executes VCN VR 277 corresponding to the VCN ofwhich compute instance 268 is a member. NVD 212 may also execute one ormore VCN VRs 283 corresponding to VCNs corresponding to the computeinstances hosted by host machines 206 and 208.

A host machine may include one or more network interface cards (NIC)that enable the host machine to be connected to other devices. A NIC ona host machine may provide one or more ports (or interfaces) that enablethe host machine to be communicatively connected to another device. Forexample, a host machine may be connected to an NVD using one or moreports (or interfaces) provided on the host machine and on the NVD. Ahost machine may also be connected to other devices such as another hostmachine.

For example, in FIG. 2 , host machine 202 is connected to NVD 210 usinglink 220 that extends between a port 234 provided by a NIC 232 of hostmachine 202 and between a port 236 of NVD 210. Host machine 206 isconnected to NVD 212 using link 224 that extends between a port 246provided by a NIC 244 of host machine 206 and between a port 248 of NVD212. Host machine 208 is connected to NVD 212 using link 226 thatextends between a port 252 provided by a NIC 250 of host machine 208 andbetween a port 254 of NVD 212.

The NVDs are in turn connected via communication links totop-of-the-rack (TOR) switches, which are connected to physical network218 (also referred to as the switch fabric). In certain embodiments, thelinks between a host machine and an NVD, and between an NVD and a TORswitch are Ethernet links. For example, in FIG. 2 , NVDs 210 and 212 areconnected to TOR switches 214 and 216, respectively, using links 228 and230. In certain embodiments, the links 220, 224, 226, 228, and 230 areEthernet links. The collection of host machines and NVDs that areconnected to a TOR is sometimes referred to as a rack.

Physical network 218 provides a communication fabric that enables TORswitches to communicate with each other. Physical network 218 can be amulti-tiered network. In certain implementations, physical network 218is a multi-tiered Clos network of switches, with TOR switches 214 and216 representing the leaf level nodes of the multi-tiered and multi-nodephysical switching network 218. Different Clos network configurationsare possible including but not limited to a 2-tier network, a 3-tiernetwork, a 4-tier network, a 5-tier network, and in general a “n”-tierednetwork. An example of a Clos network is depicted in FIG. 5 anddescribed below.

Various different connection configurations are possible between hostmachines and NVDs such as one-to-one configuration, many-to-oneconfiguration, one-to-many configuration, and others. In a one-to-oneconfiguration implementation, each host machine is connected to its ownseparate NVD. For example, in FIG. 2 , host machine 202 is connected toNVD 210 via NIC 232 of host machine 202. In a many-to-one configuration,multiple host machines are connected to one NVD. For example, in FIG. 2, host machines 206 and 208 are connected to the same NVD 212 via NICs244 and 250, respectively.

In a one-to-many configuration, one host machine is connected tomultiple NVDs. FIG. 3 shows an example within CSPI 300 where a hostmachine is connected to multiple NVDs. As shown in FIG. 3 , host machine302 comprises a network interface card (NIC) 304 that includes multipleports 306 and 308. Host machine 300 is connected to a first NVD 310 viaport 306 and link 320, and connected to a second NVD 312 via port 308and link 322. Ports 306 and 308 may be Ethernet ports and the links 320and 322 between host machine 302 and NVDs 310 and 312 may be Ethernetlinks. NVD 310 is in turn connected to a first TOR switch 314 and NVD312 is connected to a second TOR switch 316. The links between NVDs 310and 312, and TOR switches 314 and 316 may be Ethernet links. TORswitches 314 and 316 represent the Tier-0 switching devices inmulti-tiered physical network 318.

The arrangement depicted in FIG. 3 provides two separate physicalnetwork paths to and from physical switch network 318 to host machine302: a first path traversing TOR switch 314 to NVD 310 to host machine302, and a second path traversing TOR switch 316 to NVD 312 to hostmachine 302. The separate paths provide for enhanced availability(referred to as high availability) of host machine 302. If there areproblems in one of the paths (e.g., a link in one of the paths goesdown) or devices (e.g., a particular NVD is not functioning), then theother path may be used for communications to/from host machine 302.

In the configuration depicted in FIG. 3 , the host machine is connectedto two different NVDs using two different ports provided by a NIC of thehost machine. In other embodiments, a host machine may include multipleNICs that enable connectivity of the host machine to multiple NVDs.

Referring back to FIG. 2 , an NVD is a physical device or component thatperforms one or more network and/or storage virtualization functions. AnNVD may be any device with one or more processing units (e.g., CPUs,Network Processing Units (NPUs), FPGAs, packet processing pipelines,etc.), memory including cache, and ports. The various virtualizationfunctions may be performed by software/firmware executed by the one ormore processing units of the NVD.

An NVD may be implemented in various different forms. For example, incertain embodiments, an NVD is implemented as an interface card referredto as a smartNIC or an intelligent NIC with an embedded processoronboard. A smartNIC is a separate device from the NICs on the hostmachines. In FIG. 2 , the NVDs 210 and 212 may be implemented assmartNICs that are connected to host machines 202, and host machines 206and 208, respectively.

A smartNIC is however just one example of an NVD implementation. Variousother implementations are possible. For example, in some otherimplementations, an NVD or one or more functions performed by the NVDmay be incorporated into or performed by one or more host machines, oneor more TOR switches, and other components of CSPI 200. For example, anNVD may be embodied in a host machine where the functions performed byan NVD are performed by the host machine. As another example, an NVD maybe part of a TOR switch or a TOR switch may be configured to performfunctions performed by an NVD that enables the TOR switch to performvarious complex packet transformations that are used for a public cloud.A TOR that performs the functions of an NVD is sometimes referred to asa smart TOR. In yet other implementations, where virtual machines (VMs)instances, but not bare metal (BM) instances, are offered to customers,functions performed by an NVD may be implemented inside a hypervisor ofthe host machine. In some other implementations, some of the functionsof the NVD may be offloaded to a centralized service running on a fleetof host machines.

In certain embodiments, such as when implemented as a smartNIC as shownin FIG. 2 , an NVD may comprise multiple physical ports that enable itto be connected to one or more host machines and to one or more TORswitches. A port on an NVD can be classified as a host-facing port (alsoreferred to as a “south port”) or a network-facing or TOR-facing port(also referred to as a “north port”). A host-facing port of an NVD is aport that is used to connect the NVD to a host machine. Examples ofhost-facing ports in FIG. 2 include port 236 on NVD 210, and ports 248and 254 on NVD 212. A network-facing port of an NVD is a port that isused to connect the NVD to a TOR switch. Examples of network-facingports in FIG. 2 include port 256 on NVD 210, and port 258 on NVD 212. Asshown in FIG. 2 , NVD 210 is connected to TOR switch 214 using link 228that extends from port 256 of NVD 210 to the TOR switch 214. Likewise,NVD 212 is connected to TOR switch 216 using link 230 that extends fromport 258 of NVD 212 to the TOR switch 216.

An NVD receives packets and frames from a host machine (e.g., packetsand frames generated by a compute instance hosted by the host machine)via a host-facing port and, after performing the necessary packetprocessing, may forward the packets and frames to a TOR switch via anetwork-facing port of the NVD. An NVD may receive packets and framesfrom a TOR switch via a network-facing port of the NVD and, afterperforming the necessary packet processing, may forward the packets andframes to a host machine via a host-facing port of the NVD.

In certain embodiments, there may be multiple ports and associated linksbetween an NVD and a TOR switch. These ports and links may be aggregatedto form a link aggregator group of multiple ports or links (referred toas a LAG). Link aggregation allows multiple physical links between twoend-points (e.g., between an NVD and a TOR switch) to be treated as asingle logical link. All the physical links in a given LAG may operatein full-duplex mode at the same speed. LAGs help increase the bandwidthand reliability of the connection between two endpoints. If one of thephysical links in the LAG goes down, traffic is dynamically andtransparently reassigned to one of the other physical links in the LAG.The aggregated physical links deliver higher bandwidth than eachindividual link. The multiple ports associated with a LAG are treated asa single logical port. Traffic can be load-balanced across the multiplephysical links of a LAG. One or more LAGs may be configured between twoendpoints. The two endpoints may be between an NVD and a TOR switch,between a host machine and an NVD, and the like.

An NVD implements or performs network virtualization functions. Thesefunctions are performed by software/firmware executed by the NVD.Examples of network virtualization functions include without limitation:packet encapsulation and de-capsulation functions; functions forcreating a VCN network; functions for implementing network policies suchas VCN security list (firewall) functionality; functions that facilitatethe routing and forwarding of packets to and from compute instances in aVCN; and the like. In certain embodiments, upon receiving a packet, anNVD is configured to execute a packet processing pipeline for processingthe packet and determining how the packet is to be forwarded or routed.As part of this packet processing pipeline, the NVD may execute one ormore virtual functions associated with the overlay network such asexecuting VNICs associated with cis in the VCN, executing a VirtualRouter (VR) associated with the VCN, the encapsulation and decapsulationof packets to facilitate forwarding or routing in the virtual network,execution of certain gateways (e.g., the Local Peering Gateway), theimplementation of Security Lists, Network Security Groups, networkaddress translation (NAT) functionality (e.g., the translation of PublicIP to Private IP on a host by host basis), throttling functions, andother functions.

In certain embodiments, the packet processing data path in an NVD maycomprise multiple packet pipelines, each composed of a series of packettransformation stages. In certain implementations, upon receiving apacket, the packet is parsed and classified to a single pipeline. Thepacket is then processed in a linear fashion, one stage after another,until the packet is either dropped or sent out over an interface of theNVD. These stages provide basic functional packet processing buildingblocks (e.g., validating headers, enforcing throttle, inserting newLayer-2 headers, enforcing L4 firewall, VCN encapsulation/decapsulation,etc.) so that new pipelines can be constructed by composing existingstages, and new functionality can be added by creating new stages andinserting them into existing pipelines.

An NVD may perform both control plane and data plane functionscorresponding to a control plane and a data plane of a VCN. Examples ofa VCN Control Plane are also depicted in FIGS. 16, 17, 18, and 19 (seereferences 1616, 1716, 1816, and 1916) and described below. Examples ofa VCN Data Plane are depicted in FIGS. 16, 17, 18, and 19 (seereferences 1618, 1718, 1818, and 1918) and described below. The controlplane functions include functions used for configuring a network (e.g.,setting up routes and route tables, configuring VNICs, etc.) thatcontrols how data is to be forwarded. In certain embodiments, a VCNControl Plane is provided that computes all the overlay-to-substratemappings centrally and publishes them to the NVDs and to the virtualnetwork edge devices such as various gateways such as the DRG, the SGW,the IGW, etc. Firewall rules may also be published using the samemechanism. In certain embodiments, an NVD only gets the mappings thatare relevant for that NVD. The data plane functions include functionsfor the actual routing/forwarding of a packet based upon configurationset up using control plane. A VCN data plane is implemented byencapsulating the customer's network packets before they traverse thesubstrate network. The encapsulation/decapsulation functionality isimplemented on the NVDs. In certain embodiments, an NVD is configured tointercept all network packets in and out of host machines and performnetwork virtualization functions.

As indicated above, an NVD executes various virtualization functionsincluding VNICs and VCN VRs. An NVD may execute VNICs associated withthe compute instances hosted by one or more host machines connected tothe VNIC. For example, as depicted in FIG. 2 , NVD 210 executes thefunctionality for VNIC 276 that is associated with compute instance 268hosted by host machine 202 connected to NVD 210. As another example, NVD212 executes VNIC 280 that is associated with bare metal computeinstance 272 hosted by host machine 206, and executes VNIC 284 that isassociated with compute instance 274 hosted by host machine 208. A hostmachine may host compute instances belonging to different VCNs, whichbelong to different customers, and the NVD connected to the host machinemay execute the VNICs (i.e., execute VNICs-relate functionality)corresponding to the compute instances.

An NVD also executes VCN Virtual Routers corresponding to the VCNs ofthe compute instances. For example, in the embodiment depicted in FIG. 2, NVD 210 executes VCN VR 277 corresponding to the VCN to which computeinstance 268 belongs. NVD 212 executes one or more VCN VRs 283corresponding to one or more VCNs to which compute instances hosted byhost machines 206 and 208 belong. In certain embodiments, the VCN VRcorresponding to that VCN is executed by all the NVDs connected to hostmachines that host at least one compute instance belonging to that VCN.If a host machine hosts compute instances belonging to different VCNs,an NVD connected to that host machine may execute VCN VRs correspondingto those different VCNs.

In addition to VNICs and VCN VRs, an NVD may execute various software(e.g., daemons) and include one or more hardware components thatfacilitate the various network virtualization functions performed by theNVD. For purposes of simplicity, these various components are groupedtogether as “packet processing components” shown in FIG. 2 . Forexample, NVD 210 comprises packet processing components 286 and NVD 212comprises packet processing components 288. For example, the packetprocessing components for an NVD may include a packet processor that isconfigured to interact with the NVD's ports and hardware interfaces tomonitor all packets received by and communicated using the NVD and storenetwork information. The network information may, for example, includenetwork flow information identifying different network flows handled bythe NVD and per flow information (e.g., per flow statistics). In certainembodiments, network flows information may be stored on a per VNICbasis. The packet processor may perform packet-by-packet manipulationsas well as implement stateful NAT and L4 firewall (FW). As anotherexample, the packet processing components may include a replicationagent that is configured to replicate information stored by the NVD toone or more different replication target stores. As yet another example,the packet processing components may include a logging agent that isconfigured to perform logging functions for the NVD. The packetprocessing components may also include software for monitoring theperformance and health of the NVD and, also possibly of monitoring thestate and health of other components connected to the NVD.

FIG. 1 shows the components of an example virtual or overlay networkincluding a VCN, subnets within the VCN, compute instances deployed onsubnets, VNICs associated with the compute instances, a VR for a VCN,and a set of gateways configured for the VCN. The overlay componentsdepicted in FIG. 1 may be executed or hosted by one or more of thephysical components depicted in FIG. 2 . For example, the computeinstances in a VCN may be executed or hosted by one or more hostmachines depicted in FIG. 2 . For a compute instance hosted by a hostmachine, the VNIC associated with that compute instance is typicallyexecuted by an NVD connected to that host machine (i.e., the VNICfunctionality is provided by the NVD connected to that host machine).The VCN VR function for a VCN is executed by all the NVDs that areconnected to host machines hosting or executing the compute instancesthat are part of that VCN. The gateways associated with a VCN may beexecuted by one or more different types of NVDs. For example, certaingateways may be executed by smartNICs, while others may be executed byone or more host machines or other implementations of NVDs.

As described above, a compute instance in a customer VCN may communicatewith various different endpoints, where the endpoints can be within thesame subnet as the source compute instance, in a different subnet butwithin the same VCN as the source compute instance, or with an endpointthat is outside the VCN of the source compute instance. Thesecommunications are facilitated using VNICs associated with the computeinstances, the VCN VRs, and the gateways associated with the VCNs.

For communications between two compute instances on the same subnet in aVCN, the communication is facilitated using VNICs associated with thesource and destination compute instances. The source and destinationcompute instances may be hosted by the same host machine or by differenthost machines. A packet originating from a source compute instance maybe forwarded from a host machine hosting the source compute instance toan NVD connected to that host machine. On the NVD, the packet isprocessed using a packet processing pipeline, which can includeexecution of the VNIC associated with the source compute instance. Sincethe destination endpoint for the packet is within the same subnet,execution of the VNIC associated with the source compute instanceresults in the packet being forwarded to an NVD executing the VNICassociated with the destination compute instance, which then processesand forwards the packet to the destination compute instance. The VNICsassociated with the source and destination compute instances may beexecuted on the same NVD (e.g., when both the source and destinationcompute instances are hosted by the same host machine) or on differentNVDs (e.g., when the source and destination compute instances are hostedby different host machines connected to different NVDs). The VNICs mayuse routing/forwarding tables stored by the NVD to determine the nexthop for the packet.

For a packet to be communicated from a compute instance in a subnet toan endpoint in a different subnet in the same VCN, the packetoriginating from the source compute instance is communicated from thehost machine hosting the source compute instance to the NVD connected tothat host machine. On the NVD, the packet is processed using a packetprocessing pipeline, which can include execution of one or more VNICs,and the VR associated with the VCN. For example, as part of the packetprocessing pipeline, the NVD executes or invokes functionalitycorresponding to the VNIC (also referred to as executes the VNIC)associated with source compute instance. The functionality performed bythe VNIC may include looking at the VLAN tag on the packet. Since thepacket's destination is outside the subnet, the VCN VR functionality isnext invoked and executed by the NVD. The VCN VR then routes the packetto the NVD executing the VNIC associated with the destination computeinstance. The VNIC associated with the destination compute instance thenprocesses the packet and forwards the packet to the destination computeinstance. The VNICs associated with the source and destination computeinstances may be executed on the same NVD (e.g., when both the sourceand destination compute instances are hosted by the same host machine)or on different NVDs (e.g., when the source and destination computeinstances are hosted by different host machines connected to differentNVDs).

If the destination for the packet is outside the VCN of the sourcecompute instance, then the packet originating from the source computeinstance is communicated from the host machine hosting the sourcecompute instance to the NVD connected to that host machine. The NVDexecutes the VNIC associated with the source compute instance. Since thedestination end point of the packet is outside the VCN, the packet isthen processed by the VCN VR for that VCN. The NVD invokes the VCN VRfunctionality, which may result in the packet being forwarded to an NVDexecuting the appropriate gateway associated with the VCN. For example,if the destination is an endpoint within the customer's on-premisenetwork, then the packet may be forwarded by the VCN VR to the NVDexecuting the DRG gateway configured for the VCN. The VCN VR may beexecuted on the same NVD as the NVD executing the VNIC associated withthe source compute instance or by a different NVD. The gateway may beexecuted by an NVD, which may be a smartNIC, a host machine, or otherNVD implementation. The packet is then processed by the gateway andforwarded to a next hop that facilitates communication of the packet toits intended destination endpoint. For example, in the embodimentdepicted in FIG. 2 , a packet originating from compute instance 268 maybe communicated from host machine 202 to NVD 210 over link 220 (usingNIC 232). On NVD 210, VNIC 276 is invoked since it is the VNICassociated with source compute instance 268. VNIC 276 is configured toexamine the encapsulated information in the packet, and determine a nexthop for forwarding the packet with the goal of facilitatingcommunication of the packet to its intended destination endpoint, andthen forward the packet to the determined next hop.

A compute instance deployed on a VCN can communicate with variousdifferent endpoints. These endpoints may include endpoints that arehosted by CSPI 200 and endpoints outside CSPI 200. Endpoints hosted byCSPI 200 may include instances in the same VCN or other VCNs, which maybe the customer's VCNs, or VCNs not belonging to the customer.Communications between endpoints hosted by CSPI 200 may be performedover physical network 218. A compute instance may also communicate withendpoints that are not hosted by CSPI 200, or are outside CSPI 200.Examples of these endpoints include endpoints within a customer'son-premise network or data center, or public endpoints accessible over apublic network such as the Internet. Communications with endpointsoutside CSPI 200 may be performed over public networks (e.g., theInternet) (not shown in FIG. 2 ) or private networks (not shown in FIG.2 ) using various communication protocols.

The architecture of CSPI 200 depicted in FIG. 2 is merely an example andis not intended to be limiting. Variations, alternatives, andmodifications are possible in alternative embodiments. For example, insome implementations, CSPI 200 may have more or fewer systems orcomponents than those shown in FIG. 2 , may combine two or more systems,or may have a different configuration or arrangement of systems. Thesystems, subsystems, and other components depicted in FIG. 2 may beimplemented in software (e.g., code, instructions, program) executed byone or more processing units (e.g., processors, cores) of the respectivesystems, using hardware, or combinations thereof. The software may bestored on a non-transitory storage medium (e.g., on a memory device).

FIG. 4 depicts connectivity between a host machine and an NVD forproviding I/O virtualization for supporting multitenancy according tocertain embodiments. As depicted in FIG. 4 , host machine 402 executes ahypervisor 404 that provides a virtualized environment. Host machine 402executes two virtual machine instances, VM1 406 belonging tocustomer/tenant #1 and VM2 408 belonging to customer/tenant #2. Hostmachine 402 comprises a physical NIC 410 that is connected to an NVD 412via link 414. Each of the compute instances is attached to a VNIC thatis executed by NVD 412. In the embodiment in FIG. 4 , VM1 406 isattached to VNIC-VM1 420 and VM2 408 is attached to VNIC-VM2 422.

As shown in FIG. 4 , NIC 410 comprises two logical NICs, logical NIC A416 and logical NIC B 418. Each virtual machine is attached to andconfigured to work with its own logical NIC. For example, VM1 406 isattached to logical NIC A 416 and VM2 408 is attached to logical NIC B418. Even though host machine 402 comprises only one physical NIC 410that is shared by the multiple tenants, due to the logical NICs, eachtenant's virtual machine believes they have their own host machine andNIC.

In certain embodiments, each logical NIC is assigned its own VLAN ID.Thus, a specific VLAN ID is assigned to logical NIC A 416 for Tenant #1and a separate VLAN ID is assigned to logical NIC B 418 for Tenant #2.When a packet is communicated from VM1 406, a tag assigned to Tenant #1is attached to the packet by the hypervisor and the packet is thencommunicated from host machine 402 to NVD 412 over link 414. In asimilar manner, when a packet is communicated from VM2 408, a tagassigned to Tenant #2 is attached to the packet by the hypervisor andthe packet is then communicated from host machine 402 to NVD 412 overlink 414. Accordingly, a packet 424 communicated from host machine 402to NVD 412 has an associated tag 426 that identifies a specific tenantand associated VM. On the NVD, for a packet 424 received from hostmachine 402, the tag 426 associated with the packet is used to determinewhether the packet is to be processed by VNIC-VM1 420 or by VNIC-VM2422. The packet is then processed by the corresponding VNIC. Theconfiguration depicted in FIG. 4 enables each tenant's compute instanceto believe that they own their own host machine and NIC. The setupdepicted in FIG. 4 provides for I/O virtualization for supportingmulti-tenancy.

FIG. 5 depicts a simplified block diagram of a physical network 500according to certain embodiments. The embodiment depicted in FIG. 5 isstructured as a Clos network. A Clos network is a particular type ofnetwork topology designed to provide connection redundancy whilemaintaining high bisection bandwidth and maximum resource utilization. AClos network is a type of non-blocking, multistage or multi-tieredswitching network, where the number of stages or tiers can be two,three, four, five, etc. The embodiment depicted in FIG. 5 is a 3-tierednetwork comprising tiers 1, 2, and 3. The TOR switches 504 representTier-0 switches in the Clos network. One or more NVDs are connected tothe TOR switches. Tier-0 switches are also referred to as edge devicesof the physical network. The Tier-0 switches are connected to Tier-1switches, which are also referred to as leaf switches. In the embodimentdepicted in FIG. 5 , a set of “n” Tier-0 TOR switches are connected to aset of “n” Tier-1 switches and together form a pod. Each Tier-0 switchin a pod is interconnected to all the Tier-1 switches in the pod, butthere is no connectivity of switches between pods. In certainimplementations, two pods are referred to as a block. Each block isserved by or connected to a set of “n” Tier-2 switches (sometimesreferred to as spine switches). There can be several blocks in thephysical network topology. The Tier-2 switches are in turn connected to“n” Tier-3 switches (sometimes referred to as super-spine switches).Communication of packets over physical network 500 is typicallyperformed using one or more Layer-3 communication protocols. Typically,all the layers of the physical network, except for the TORs layer aren-ways redundant thus allowing for high availability. Policies may bespecified for pods and blocks to control the visibility of switches toeach other in the physical network so as to enable scaling of thephysical network.

A feature of a Clos network is that the maximum hop count to reach fromone Tier-0 switch to another Tier-0 switch (or from an NVD connected toa Tier-0-switch to another NVD connected to a Tier-0 switch) is fixed.For example, in a 3-Tiered Clos network at most seven hops are neededfor a packet to reach from one NVD to another NVD, where the source andtarget NVDs are connected to the leaf tier of the Clos network.Likewise, in a 4-tiered Clos network, at most nine hops are needed for apacket to reach from one NVD to another NVD, where the source and targetNVDs are connected to the leaf tier of the Clos network. Thus, a Closnetwork architecture maintains consistent latency throughout thenetwork, which is important for communication within and between datacenters. A Clos topology scales horizontally and is cost effective. Thebandwidth/throughput capacity of the network can be easily increased byadding more switches at the various tiers (e.g., more leaf and spineswitches) and by increasing the number of links between the switches atadjacent tiers.

In certain embodiments, each resource within CSPI is assigned a uniqueidentifier called a Cloud Identifier (CID). This identifier is includedas part of the resource's information and can be used to manage theresource, for example, via a Console or through APIs. An example syntaxfor a CID is:

-   -   ocid1.<RESOURCE TYPE>.<REALM>. [REGION][.FUTURE USE].<UNIQUE ID>        where,    -   ocid1: The literal string indicating the version of the CID;    -   resource type: The type of resource (for example, instance,        volume, VCN, subnet, user, group, and so on);    -   realm: The realm the resource is in. Example values are “c1” for        the commercial realm, “c2” for the Government Cloud realm, or        “c3” for the Federal Government Cloud realm, etc. Each realm may        have its own domain name;    -   region: The region the resource is in. If the region is not        applicable to the resource, this part might be blank;    -   future use: Reserved for future use.    -   unique ID: The unique portion of the ID. The format may vary        depending on the type of resource or service.

Examples of Loop Prevention

FIG. 6 illustrates an example of a VCN 600 configured and deployed for acustomer, such as an enterprise according to certain embodiments. TheVCN 600 includes a virtual L2 network 610 and may be implemented in theOracle Cloud Infrastructure (OCI).

Generally, the VCN 600 may be a software-defined virtual version of atraditional network, including subnets, route tables, and gateways, onwhich various compute instances 620A, 620B, through 620K may run(referred to herein collectively as “compute instances 620” orindividually as a “compute instance 620”). For example, the VCN 600 is avirtual, private network that the customer sets up in a cloudinfrastructure. The cloud infrastructure may reside within a particularregion, and it includes all the region's availability domains. A subnetis a subdivision of the VCN 600. Each subnet defined in the cloudinfrastructure can either be in a single availability domain or span allthe availability domains in the region. At least one cloudinfrastructure may need to be set up before a compute instance 620 canbe launched. The cloud infrastructure can be configured with an optionalInternet gateway to handle public traffic, as well as an optional IPsecurity (IPSec), virtual private network (VPN) connection, or OCIFastConnect to securely extend a customer's on-premises network. The VCN600 can be privately connected to another VCN such that the traffic doesnot traverse the Internet. The Classless Inter-Domain Routing (CIDR) forthe two VCNs may not overlap.

In the illustration of FIG. 6 , the virtual L2 network 610 supports anyof the above virtual networking and is implemented as an overlay on thecloud infrastructure, where the overlay implements the L2 protocols. Thecompute instances 620 can belong to and be connected via the virtual L2network 610 using the L2 protocols. In particular, the virtual L2network 610 may include virtual switches, VNICs, and/or other virtualcomputing resources for receiving and routing frames from and/to thecompute instances 620. The overlay implements this virtualization on theunderlying computing resources of the cloud infrastructure.

For example, the compute instance 620A is hosted on a first host machinethat is connected to a NVD via a first port. The NVD hosts a first VNICfor the compute instance 620A, where this first VNIC is a component ofthe virtual L2 network 610. To transmit a frame to the compute instance620K, the compute instance 620A includes, in the frame, a MAC address ofthe compute instance 620A as a source address and a MAC address of thecompute instance 620K as the destination address according to the L2protocol. These MAC addresses may be referred to also as overlay MACaddresses or logical MAC addresses. The frame is received by the virtualL2 network 610 via the first VNIC and sent to a second VNIC thatcorresponds to the compute instance 620K. In effect, the first hostmachine forwards the frame to the NVD via the first port and the NVDroutes the frame to a second host machine of the compute instance 620K.The routing includes encapsulating the frame with the relevantinformation (e.g., MAC addresses of the host machines, which may bereferred to also as physical MAC addresses or substrate MAC addresses).

FIG. 7 illustrates an example of a VCN 700 that includes virtual L2 andlayer 3 (L3) networks set up for a customer according to certainembodiments. In an example, the VCN 700 includes a virtual L3 network710. The virtual L3 network 710 may be a virtual network that implementsprotocols of the L3 layer of the OSI model and within which multiplesubnets 712A through 712N can be set-up (referred to herein collectivelyas “subnets 712” or individually as a “subnet 712”). In addition, theVCN 700 includes a virtual L2 network 720 that implements protocols ofthe L2 layer of the OSI model, such as the virtual L2 network 610 ofFIG. 6 . A switched virtual interface (SVI) router 730 connects thevirtual L3 network 710 and the virtual L2 network 720. The virtual L2network 720 may have a designated SVI IP address. Traffic betweensubnets may go through SVI router 730.

In the virtual L3 network, each subnet 712 may have a contiguous rangeof IP version 4 (IPv4) or version 6 (IPv6) addresses (for example,10.0.0.0/24 and 10.0.1.0/24) that do not overlap with other subnets inthe VCN 700. Subnets act as a unit of configuration. All computeinstances in a given subnet use the same route table, security lists,and Dynamic Host Configuration Protocol (DHCP) options. Subnets 712 canalso include VNICs. Each compute instance 620 may be attached to a VNICwhich may reside in a subnet and enable a network connection for thecompute instance 620. Subnets can be either public or private. A privatesubnet may have VNICs that do not have public internet protocol (IP)addresses. A public subnet may have VNICs that can have public IPaddresses. A subnet may exist either in a single availability domain oracross multiple availability domains in a particular region.

In the virtual L2 network, VNICs may also be attached to computeinstances, to enable communications between the computing instancesusing the L2 protocols. Whether in L2 or L3, a VNIC may determine how acompute instance 620 connects with endpoints and can be hosted on a NVD(also known as intelligent server adapter (ISA)). L2 VNICs enablecommunications between compute instances using the L2 protocols. WhereasL3 VNICs enable the communications using the L3 protocols.

Each compute instance 620 may have a primary VNIC that is created duringcompute instance launch and may not be removed. Secondary VNICs (in thesame availability domain as the primary VNIC) may be added to anexisting compute instance 620 and may be removed as desired.

An L2 VNIC may be hosted on a NVD that implements switch functions. ANVD may gradually learn the source MAC addresses of compute instancesbased on incoming frames from the sources, maintain an L2 forwardingtable, and transmit frames based on the MAC addresses and the forwardingtable. Transmitting a frame includes transmitting the actual frame(e.g., forwarding the frame) or one or more replicas of the frame (e.g.,broadcasting the frame). For example, when receiving a frame with asource MAC address from a port, the NVD may learn that frames to thesource MAC address can be sent through the port. The NVD may also cacheand age out MAC addresses. The NVD may keep a static (non-aged) MACaddress of the SVI router 730. When receiving frames with unknowndestination MAC addresses or with broadcast destination MAC addresses,the NVD may broadcast (flood) these frames.

Generally, the OSI model contains seven layers. Layer one (L1) is thephysical layer associated with the transmission of data bits overphysical mediums. L2 is the data link layer, which specifiestransmission of frames between connected nodes on the physical layer. L3is the network layer, which describes the addressing, routing, andtraffic control of a multi-node network.

L2 is a broadcast MAC-level network, while L3 is a segmented routingover IP networks. L2 may include two sublayers, where the MAC layerapproves devices to access and transmit media, and the Logical LinkLayer (LLC) is responsible for managing communication links and handlingframe traffic, such as identifying protocols on the network layer andchecking for errors and frame synchronization. While L3 works with IPaddresses, L2 works with MAC addresses. MAC addresses are uniqueidentifiers for the network adapter present in each device. IP addressesare a layer of abstraction higher than MAC addresses, and thus may beslower. IP addresses are generally “leased” or “assigned” by a DHCPserver and can be changed, while a MAC address is a fixed address of thenetwork adapter and may not be changed on a device without changing thehardware adapter. A frame is a protocol data unit on an L2 network.Frames have a defined structure and can be used for error detection,control plane activities, and the like. The network may use some framesto control the data link itself.

At L2, unicast refers to sending frames from one node to a single othernode, multicast refers to sending traffic from one node to multiplenodes, and broadcast refers to the transmission of frames to all nodesin a network. A broadcast domain is a logical division of a network inwhich all nodes of that network can be reached at L2 by a broadcast.Segments of a LAN can be linked at the frame level using bridges.Bridging creates separate broadcast domains on the LAN, creating VLANs,which are independent logical networks that group together relateddevices into separate network segments. The grouping of devices on aVLAN is independent of where the devices are physically located in theLAN. On a VLAN, a frame whose origin and destination are in the sameVLAN are forwarded only within the local VLAN.

An L2 network device is a multiport device that uses hardware addressesand MAC addresses to process and forward data at the data link layer.Frames are sent to a specific switch port based on destination MACaddresses. L2 switches may learn MAC addresses automatically, building atable which can be used to selectively forward frames. For example, if aswitch receives frames from MAC address X on Port 1, the switch may thenknow that frames destined for MAC address X can be forwarded out of Port1 rather than having to try each available port. Because L2 informationis easily retrieved, frames can be forwarded (switched) very quickly,typically at the wire speed of the network. Devices in the same L2segment do not need routing to reach local peers. Therefore, L2switching has little or no impact on network performance or bandwidth.Additionally, L2 switches are cheap and easy to deploy. However, L2switches may not apply any intelligence when forwarding frames. Forexample, L2 switches may not natively allow multipath and may sufferfrom looping issues because L2 control protocol may not inherently haveloop prevention mechanisms. They may not route frames based on IPaddress or prioritize frames sent by particular applications. In L3networks, packets are sent to a specific next-hop IP address, based onthe destination IP address. L3 virtual networks (e.g., L3 VCN) can scalebetter, can natively support multipath, and may not suffer from loops.But many enterprise workloads still use L2 virtual networks (L2 VLANs),at least because L2 virtual networks can provide simple, inexpensive,high-performance connectivity for hundreds or even thousands of endstations.

Because an L2 network implements L2 protocols and because the L2protocols do not natively prevent looping, an L2 network can besusceptible to broadcast storms if loops are introduced. In comparison,the L3 network may not be susceptible to looping issues. Further, bothL2 and L3 networks may need to include multipath to provide redundantpaths in case of a link failure. STP can be implemented in an L2 networkto mitigate the looping issue. However, doing so may prevent multipathin the L2 network.

In particular, the STP may regulate interconnects between switches andmay disable certain links so that the resulting L2 network is a treedefining single path that avoids loops. The STP is a network protocolthat builds a loop-free logical topology for a network. The need for theSTP arises because switches in LANs are often interconnected usingredundant links to improve resilience should one connection fail.However, this connection configuration creates a switching loopresulting in broadcast radiations and MAC table instability. Ifredundant links are used to connect switches, then switching loops needto be avoided. Thus, STP is generally implemented on switches to monitorthe network topology. The basic function of STP is to prevent bridgeloops and the broadcast radiation that results from them. Spanning treealso allows a network design to include backup links providing faulttolerance if an active link fails. STP creates a spanning tree thatcharacterizes the relationship of nodes within a network of connected L2switches or bridges. STP disables links that are not part of thespanning tree, leaving a single active path between any two networknodes, such as between the tree root and any leaf. All other paths areforced into a standby (or blocked) state. STP-based L2 loop preventionmay be achieved using various flavors or extensions of STPs, such asRapid Spanning Tree Protocol (RSTP), Multiple Spanning Tree Protocol(MSTP), and VLAN Spanning Tree Protocol (VSTP).

Thus, for L2 networks, the use of STP may not support an optimizedimplementation because of the resulting multipath prevention. A virtualL2 network, such as the virtual L2 network 720, is implemented as anoverlay of an L2 network on a cloud infrastructure. As such, the virtualL2 network is also susceptible to looping issues. STP can also beimplemented in the virtual L2 network, but would likewise result in aloss of the multipath capability. Embodiments of the present disclosuresupport loop prevention and multipath, as further described inconnection with the next figures.

FIG. 8 illustrates an example of an infrastructure that supports avirtual L2 network of a VCN according to certain embodiments. Thecomponents depicted in FIG. 8 are generally provided by a CSP and arepart of its CSPI that is used to provide cloud services (e.g., IaaSservices) to a subscribing customer. In an example, the components arethe same or similar to the components described in the architecturaldiagram of FIG. 2 . Similarities between the components of the twofigures are not repeated herein in the interest of brevity.

As depicted in FIG. 8 , a host machine 820A is connected to an NVD 810A,which in turn is connected to a TOR switch 832A of a physical switchnetwork 830. Further, host machines 820A through 820L (referred toherein collectively as “hosts 820” or individually as a “host 820”) areconnected to NVD 810A via Ethernet links, and NVD 810A is connected tothe TOR switch 832A via another Ethernet link. As also depicted in FIG.8 , host machines 821A through 821L (referred to herein collectively as“hosts 821” or individually as a “host 821”) are connected to an NVD810K via an Ethernet link, and the NVD 810 K is connected to a TORswitch 832K via an Ethernet link.

Each host 820 or 821 may execute one or more compute instances for oneor more customers. The compute instances for a customer may be part ofone or more virtual cloud networks (VCNs) configured by the customer andhosted by in the cloud by the CSPI. Each one of the NVDs 810 can alsohost one or more VNICs for each of the compute instances. The computeinstances of the customer are connected, via the VNICs, to a virtual L2network, such as the virtual L2 network 610 of FIG. 6 or the L2 virtualnetwork 720 of FIG. 7 . This virtual L2 network may be implemented as anoverlay on the infrastructure that includes the NVDs 810, the hosts 820and 821, and the switch network 830.

In the illustration of FIG. 8 , the NVD 810A includes a north port 812that connects the NVD 810A to the TOR switch 832A. The NVD 810A alsoincludes a set of south ports 814A through 814L, each of which isconnected to one of the hosts 820A through 820L. Further, the NVD 810Ahosts a plurality of VNICs 816A through 816M, each of which is attachedto a compute instance executing on a host 820.

Also in the illustration of FIG. 8 , the host 820A is connected to theNVD 810A via the south port 814A. The host 820A may can execute acompute instance 822A for the customer. The VNIC 816A hosted on the NVD810A corresponds to the compute instance 822A. The compute instance 822Acan belong to a virtual L2 network within a VCN of the customer.Similarly, the host 820L is connected to the NVD 810A via the south port814L and hosts at least a compute instance 822M for the customer, wherethe VNIC 816M corresponds to this compute instance 822M. Although FIG. 8illustrates that each host 820 is connected to a single NVD (e.g., theNVD 810A), some or all of the hosts 820 may connect to multiple NVDs.

The NVD 810K may be similar to the NVD 810A. In particular, the NVD 810Kincludes a north port 813 that connects the NVD 810K to a TOR switch832K of the switch network 830. The NVD 810K also includes a set ofsouth ports 815A through 815L, each of which is connected to one of thehosts 821A through 821L. Further, the NVD 810K hosts a plurality ofVNICs 817A through 817M, each of which is attached to a compute instanceexecuting on a host 821. The host 821A is connected to the NVD 810K viathe south port 815A and hosts a compute instance 823A for the customer.The VNIC 817A host corresponds to the compute instance 823A. Similarly,the host 821L is connected to the NVD 810K via the south port 815L andhosts at least a compute instance 823M for the customer, where the VNIC817M corresponds to this compute instance 823M. Although FIG. 8illustrates the same number of ports, the same number of hosts, the samenumber of VNICs, and the same number of compute instances for each ofthe NVDs 810A and 810K, each of these numbers can differ.

A frame transmitted from a first compute instance to a second computeinstance is processed at the virtual level and the hardware level. Inparticular, the first compute instance 822A generates the frame thatincludes a payload, a MAC address of the first compute instance as asource address, and a MAC address of the second compute instance as adestination address. These MAC addresses are in the virtual network andare thus overlay MAC addresses. The NVD 810A receives the frame andbased on the physical or virtual port (e.g., VLAN) maps it to thecorrect VNIC (e.g., VNIC 816A). The NVD 810A then performs the necessaryoverlay functions including packet filtering, logging, destinationaddress lookup and overlay encapsulation. For example, the first NVD810A uses the overlay, destination MAC address from the frame todetermine, from a forwarding table of the NVD 810A, a physical MACaddress of a second host and a port via which the frame can be sent. Ifthis information is found in the forwarding table, the NVD 810Areplaces, in the frame, the physical MAC address of the host 820A withits MAC address as the source and its MAC address with the physical MACaddress of the second host as the destination and transmits the framevia the port. If this information is not found in the forwarding table,the NVD 810A determines that the frame is to be flooded and,accordingly, replaces, in the frame, the physical MAC address of thefirst host 820A with its MAC address as the source and its MAC addresswith a broadcast MAC address as the destination and broadcasts theframe. Transmitting a frame can include transmitting the actual frame ortransmitting multiple replicas thereof (equivalent to broadcasting theframe).

Conversely, upon receiving a frame via a north port, the NVD 810Aperforms the necessary packet transformations including frame filtering,logging, source and/or destination MAC address lookups, decapsulationand encapsulation. The result of these transformations is that the NVD810A determines which VNIC the packet belongs to and whether the packetis legitimate. If the frame passes the lookup process in the forwardingtable, the NVD 810A determines the relevant port (or VNIC and VLAN)sends the frame to the host via the port. Here also, the VNICcorresponding to the compute instance can receive and process the framemaking changes to the overlay addresses included in the frame. If nomatch is found in the forwarding table, the NVD 810A determines that theframe is to be flooded to the host facing port.

FIG. 9 illustrates an example of a loop 900 between NVDs according tocertain embodiments. The loop 900 may occur and grow exponentiallybetween the NVD 810A and the NVD 810K of the infrastructure described inFIG. 8 . In particular, a frame is received by the NVD 810A and has adestination MAC address that is not included in a forwarding table ofthe NVD 810A. In this case, the receiving NVD 810A may flood this frame(e.g., send the frame to all of the NVDs serving this VLAN for this VCNor this customer). If NVD 810K also does not have a forwarding tableentry for this destination MAC address, it too would have to flood thisframe. Because of the flooding, the frame is sent back to the originalsending NVD 810A, thereby creating a loop between these two NVDs 810Aand 810K. Upon resending the frame again, the broadcast may re-occur,thereby growing the loop. Within a short period of time (e.g., a fewmilliseconds), the growth may significantly flood the network andconsume network bandwidth.

In the example of FIG. 9 , a frame 910 is generated by a first computeinstance executing on the host 820A (e.g., the compute instance 822A)and is sent to a second compute instance executing on the host 821A(e.g., the compute instance 823A). The frame is an L2 frame thatincludes a L2 header and a payload. The payload includes an L2 protocoldata unit (L2 PDU). The header includes a first MAC address of the firstcompute instance as the source address (illustrated in FIG. 9 as “MAC1”) and a second MAC address of the second compute instance as thedestination address (illustrated in FIG. 9 as “MAC 3”). Nonetheless,embodiments of the present disclosure are not limited as such and theframe or other frames can be sent between two compute instancesexecuting on the same host, executing on different hosts connected tothe same NVD, and/or executing on different hosts connected to differentNVDs. In all these cases, the frame transmission may similarly result inthe loop 900.

The host 820A sends the frame 910 to the NVD 810A via the south port814A. The NVD 810 looks up a forwarding table and does not identify amatch between the second MAC address and an entry in this table.Accordingly, the NVD 810A determines to flood the frame 910 forcontaining an unknown destination MAC address. The flooding can involvetransmitting the frame 910 via all ports of the NVD 810A.

As such, the host 820L receives the frame 910 (e.g., a replica of thisframe 910) that includes the second MAC address. Because this second MACaddress does not correspond to a MAC address of a compute instancehosted by the host 820L, the frame replica 930 is dropped.

The NVD 810K receives the frame 910 (e.g., a replica of this frame thathas been encapsulated with the proper information for routing throughthe switch network 830 by, including, for instance, an overlay header(illustrated in the FIGS. as “O.H.”); the overlay header can include aVCN header, source and destination IP addresses, and source anddestination MAC addresses). Here, although the received frame includesthe second MAC address, and this second MAC address corresponds to thesecond compute instance that is executing on the host 821A, the NVD 810Khas not already learned and does not have an entry of the second MACaddress in its forwarding table. Accordingly, the NVD 810K alsodetermines that the received frame is to be flooded and broadcasts thereceived frame via its ports. As a result, each of the hosts 821receives the frame 910 (e.g., a replica of this frame 910). The receivedframe is dropped unless its destination MAC address matches thedestination MAC address of a compute instance on a host 821.

In addition, the flooding by the NVD 810K includes transmitting theframe 910 (or a replica thereof encapsulated with the proper informationfor routing through the switch network 830) via the north port 813,through the switch network 830, and back to the NVD 810A. Theretransmission of the frame 910 by the NVD 810A to the NVD 810K and thetransmission back of the frame 910 by the NVD 810AK to the NVD 810Agenerates the loop 900. The looping can be repeated multiple timeswithin a short period, resulting in a significant network bandwidthusage.

FIG. 10 illustrates an example of preventing a loop between NVDsassociated with a virtual L2 network according to certain embodiments.In the interest of clarity, reference is made to the NVD 810A and theNVD 810K of the infrastructure described in FIG. 8 . However, the loopprevention can apply to any other loops between network resourcessupporting a virtual L2 network, such as switches ands. Unlike FIG. 9 ,each of the NVDs implement a loop prevention rule that mitigatesoccurrences of loops. A loop prevention rule is a rule that, whenapplied, prevents one or more loops from being generated within anetwork. The loop prevention rule can specify one or more parameters andone more actions that are applied to support this loop prevention. Theparameter(s) and action(s) can be coded as, for instance, a set ofif-then statements. In an example, the loop prevention rule specifiesthat if a frame is received by a network resource via a port of thenetwork resource, the network resource cannot transmit the frame via thesame port. In particular, when the network resource broadcasts the framebecause, for instance, the frame has a destination MAC address with nomatch in a forwarding table of the network resource, the broadcastcannot occur via the port on which the frame was received.

In the illustration of FIG. 10 , the NVD 810 stores a loop preventionrule 1012A. A frame 1010 is generated by a first compute instanceexecuting on the host 820A (e.g., the compute instance 822A) and is sentto a second compute instance executing on the host 821A (e.g., thecompute instance 823A). The frame is an L2 frame that includes a headerand a payload. The payload includes an L2 PDU. The header includes afirst MAC address of the first compute instance as the source address(illustrated in FIG. 10 as “MAC 1”) and a second MAC address of thesecond compute instance as the destination address (illustrated in FIG.10 as “MAC 3”). Nonetheless, embodiments of the present disclosure arenot limited as such and the frame or other frames can be sent betweentwo compute instances executing on the same host, executing on differenthosts connected to the same NVD, and/or executing on different hostsconnected to different NVDs.

The host 820A sends the frame 1010 to the NVD 810A via the south port814A. The NVD 810A looks up its forwarding table 1014A and does notidentify a match between the second MAC address and an entry in thistable. At this point, the NVD 810A learns that the first MAC address isassociated with the south port 814A and updates its forwarding table1014A to store this association. Further, the NVD 810A broadcasts theframe 1010 via its south ports 814 (except the south port 814A) and thenorth port 812.

The host 820L receives the frame 1010 that includes the second MACaddress. Because this second MAC address does not correspond to a MACaddress of a compute instance hosted by the host 820L, the frame replicais dropped.

Further, the NVD 810K receives the frame 1010 (or a replica of the frame1010 with the proper encapsulation) via the north port 813. The NVD 810Kstores a loop prevention rule 1012K specifying that a frame received viaa port cannot be transmitted back via the same port. Here, although thereceived frames includes the second MAC address, and this second MACaddress corresponds to the second compute instance that is executing onthe host 821A, the NVD 810K has not already learned and does not have anentry of the second MAC address in its forwarding table 1014K. At thispoint, the NVD 810K learns that the first MAC address is associated withthe north port 813 and updates its forwarding table 1014K to store thisassociation. Further, the NVD 810K determines that the received frame isto be flooded because of the unknown destination MAC address and,accordingly, broadcasts this frame via its ports except the north port813 based on the loop prevention rule 1012K. As a result, the hosts 821receive the frame 1010 (or replicas thereof). As a result, each of thehosts 821 receives the frame 1010 (e.g., a replica of this frame 1010).The received frame is dropped unless its destination MAC address matchesthe destination MAC address of a compute instance on a host 821. Becauseof the loop prevention rule 1012K, the NVD 810K does not transmit backthe frame 1010 to the NVD 1010A via the north port 813. Accordingly, aloop between the NVD 810A and the NVD 810K is prevented.

The above described loops can occur not just for “unknown unicastdestination MAC addresses,” but also for “Broadcast MAC addresses.”Since “Broadcast MAC addresses” by their very definition are sent on allports, they can lead to the same loop as described above. The abovedescribed loop prevention mechanism can also be applied to such“Broadcast MAC addresses.”

FIG. 11 illustrates an example of a loop 1100 between a NVD and acompute instance executing on a host according to certain embodiments.In the interest of clarity, reference is made to the NVD 810A, the host820A, and the compute instance 822A of the infrastructure described inFIG. 8 . However, a loop can exist between the NVD and other computeinstances and/or between the compute instance and other NVDs. In anexample, the NVD 810A sends a frame 1110 addressed to the MAC address ofthe compute instance 822A. The frame is sent to the host 820A via thesouth port 814A. Upon receiving the frame 1110, and due to a softwarebug or software code of the compute instance 822A, the compute instance822A replicates and sends the frame 1110 back to the host 820A (shown asa frame 1120 in FIG. 11 ). In turn, the host 820A sends the frame 1120to the NVD 810A that receives it via the south port 814A. Thus, the loop1100 exists, where the NVD 810A receives back a frame it sent via thesouth port 814A.

FIG. 12 illustrates an example of preventing a loop between a NVD and acompute instance executing on a host according to certain embodiments.Here also in the interest of clarity of explanation, reference is madeto the NVD 810A, the host 820A, and the compute instance 822A of theinfrastructure described in FIG. 8 . However, the loop preventionsimilarly apply to any other NVD. In an example, the NVD 810A implementsa lightweight STP 1200 for each south port of the NVD 810A. In theillustration of FIG. 12 , the lightweight STP 1200 manages the southport 814A. Further, a similar lightweight STP can be implemented foreach of the remaining south ports.

Management of the south port 814A includes determining whether a loopexists (such as the loop 1100 exists) and disabling 1202 the south port814A if so. Disabling 1202 the south port 814A can include storing aflag indicating the loop and deactivating the south port 814A. The flagcan be stored in an entry associated with the MAC address of the computeinstance 822A, such as in the forwarding table 1014A of the NVD 810A.Deactivating can be implemented using multiple techniques. In onetechnique, the NVD 810A disconnects the south port 814A via softwarecontrol. In an additional or alternative technique, the NVD 810A stopsthe transmission of frames via the south port 814A and ignores framesreceived via the south port 814A. The deactivation can apply to allframes sent to or from the host 820A via the south port 814A regardlessof the specific compute instances hosted by the host 820A.Alternatively, the deactivation can apply to only the frames sent to orfrom the compute instance 822A.

To determine whether a loop exists, the lightweight STP 1200 may specifythat a frame 1210 needs to be transmitted via the south port 814A. Thetransmission can be triggered periodically, upon a launch of the computeinstance 822A, upon an update to the compute instance 822A, and/or uponthe frame congestion to and/or from the NVD 810A reaching a congestionlevel. The frame 1210 can be a BDPU. If the loop exists, the computeinstance 822A replicates the BPDU and the resulting frame 1220 is sentby the host 820A to the NVD 810A. The lightweight STP 1200 detects thatthe received frame 1220 is a BPDU and, accordingly, determines theexistence of the loop and disables 1202 the south port 814A. If no loopexists, a frame received via the south port 814A is not a BPDU and thelightweight STP 1200 can distinguish between such a frame and the BPDU.As a result, the south port 814 remains enabled.

FIGS. 13-15 illustrate examples of flows for preventing loops whileallowing multipath. Operations of the flows can be performed by a NVD.Some or all of the instructions for performing the operations of flowscan be implemented as hardware circuitry and/or stored ascomputer-readable instructions on a non-transitory computer-readablemedium of the NVD. As implemented, the instructions represent modulesthat include circuitry or code executable by processors of the NVD. Theuse of such instructions configures the NVD to perform the specificoperations described herein. Each circuitry or code in combination withthe relevant processor(s) represent a means for performing a respectiveoperation(s). While the operations are illustrated in a particularorder, it should be understood that no particular order is necessary andthat one or more operations may be omitted, skipped, performed inparallel, and/or reordered.

FIG. 13 depicts an example of a flow for preventing loops associatedwith a virtual L2 network, such as the virtual L2 network 610 of FIG. 6or the virtual L2 network 720 of FIG. 7 . A NVD can belong to a cloudinfrastructure that provides the virtual L2 network. The flow may startat operation 1302, where the NVD stores a loop prevention rule. The loopprevention rule may indicate that a frame received by the NVD via a portof the NVD may not be transmitted by the NVD via the port. At operation1304, the NVD may maintain a forwarding table. For instance, theforwarding table may include entries, each associating a port and with aMAC address of a compute instance and/or a MAC address of a host of thecompute instance. The forwarding table is usable to forward a frame thatis received by the NVD and that includes a destination MAC address. Inparticular, if the destination MAC address matches an entry in theforwarding table, the NVD forwards the frame based on the association inthe entry. Otherwise, the NVD transmits the frame via all ports exceptthe port via which the frame was received per the loop prevention rule.At operation 1306, the NVD maintains a lightweight spanning tree persouth port. The lightweight STP may rely on the transmission of a BPDUand a reception of the BPDU back to detect a loop and disable the southport. At operation 1308, the NVD routes frames based on the loopprevention rule, the forwarding table, and the lightweight spanningtrees. In this way, frames received via one or more north ports of theNVD are not looped back via these ports when their destination MACaddresses do not match entries in the forwarding table. Additionally,loops generated because of software bugs or software codes of computeinstances are detected and managed.

FIG. 14 depicts an example of a flow for preventing loops between NVDsassociated with a virtual L2 network. Here, a first NVD is connectedwith a second NVD via a switch network, where frames can be exchangedbetween the two NVDs via their relevant north ports. Each of the twoNVDs may store a loop prevention rule. The flow is described inconnection with operations of the first NVD and can similarly apply tothe operations of the second NVD.

As illustrated, the flow may start at operation 1402, where the firstNVD may receive a frame via a first port of the first NVD (e.g., a northport when the frame is received from the second NVD). The frame may haveoriginated from a second compute instance and may include an L2 PDU, afirst MAC address of the first compute instance as a destination address(e.g. a destination of the first frame), and a second MAC address of thesecond compute instance as a source address (e.g., as a source of thefirst frame). The first compute instance and the second compute instanceare members of a virtual L2 network. The first compute instance ishosted by a first host machine that is connected with the networkinterface card via a second port. At operation 1404, the first NVD maylook up its forwarding table. The look up may use the MAC addresses todetermine whether matches between the MAC addresses from the first frameand entries in the forwarding table exists. At operation 1406, the firstNVD determines whether the second MAC address matches an entry in theforwarding table. If so, the flow moves to operation 1408. Otherwise,the flow moves to operation 1420, where the first NVD updates itsforwarding table by including an entry that associates the second MACaddress with the first port, such that if a subsequent frame is receivedand includes the second MAC address as the destination address, thisframe can be forwarded via the first port. At operation 1408, the firstNVD determines whether the first MAC address matches an entry in theforwarding table. If not, the flow moves to operation 1410. Otherwise,the flow moves to operation 1430, where the first NVD forwards the firstframe to the destination (e.g., to the first compute instance, bytransmitting the first frame via the second port). At operation 1410,the first NVD determines that the first frame is to be transmitted viaall ports of the network interface card based on the second MAC address.In other words, because no destination match exits, the first NVDdetermines that it needs to flood the first frame by broadcasting it viaits ports. At operation 1412, the first NVD determines that its loopprevention rule prevents transmission of a frame using a port via whichthe frame was received. Accordingly, this loop prevention rule preventsthe first NVD from sending the first frame via the first port. Atoperation 1414, the NVD transmits the first frame via all ports of thenetwork interface card except the first port based on the loopprevention rule. In other words, by applying the loop prevention rule,the first frame is broadcasted via all the ports of the first NVD exceptfor the first port.

FIG. 15 depicts an example of a flow for preventing loops between a NVDa compute instance associated with a virtual L2 network. The flowsimilarly applies to preventing loops between the NVD and other computeinstances hosted on or more hosts that are connected with the NVDs viasouth ports of the NVD. The example flow may start at operation 1502,where the NVD transmits a first frame via a first port of the NVD (e.g.,a south port). This port is connected with a host of the computeinstance. The first frame can be a BPDU and can be transmitted based ona lightweight STP implemented on the NVD. At operation 1504, the NVDreceives a second frame via the first port. At operation 1506, the NVDdetermines whether the second frame is a replica of the first frame. Forinstance, if the second frame is also the BPDU it had sent (e.g., theBPDU is received back at operation 1504 and the BPDU has its own MACaddress as the Bridge ID inside the BPDU), the NVD determines that areplica exists and operation 1520 follows operation 1506. Otherwise, noreplica is determined and operation 1510 follows operation 1506. Atoperation 1510, the NVD does not disable the first port because no loopexists. In comparison, at operation 1520, the NVD determines that a loopexists. At operation 1522, the NVD determines a loop prevention ruleindicating one or more actions to be performed to manage the loop. Forexample, this rule is stored by the NVD and specifies that a port of theNVD via which a loop occurs is to be disabled. At operation 1524, theNVD performs an action (or all actions) based on the loop preventionrule to prevent the loop. For example, the NVD disables the first port.

Example Infrastructure as a Service Architectures

As noted above, infrastructure as a service (IaaS) is one particulartype of cloud computing. IaaS can be configured to provide virtualizedcomputing resources over a public network (e.g., the Internet). In anIaaS model, a cloud computing provider can host the infrastructurecomponents (e.g., servers, storage devices, network nodes (e.g.,hardware), deployment software, platform virtualization (e.g., ahypervisor layer), or the like). In some cases, an IaaS provider mayalso supply a variety of services to accompany those infrastructurecomponents (e.g., billing, monitoring, logging, security, load balancingand clustering, etc.). Thus, as these services may be policy-driven,IaaS users may be able to implement policies to drive load balancing tomaintain application availability and performance.

In some instances, IaaS customers may access resources and servicesthrough a wide area network (WAN), such as the Internet, and can use thecloud provider's services to install the remaining elements of anapplication stack. For example, the user can log in to the IaaS platformto create virtual machines (VMs), install operating systems (OSs) oneach VM, deploy middleware such as databases, create storage buckets forworkloads and backups, and even install enterprise software into thatVM. Customers can then use the provider's services to perform variousfunctions, including balancing network traffic, troubleshootingapplication issues, monitoring performance, managing disaster recovery,etc.

In most cases, a cloud computing model will require the participation ofa cloud provider. The cloud provider may, but need not be, a third-partyservice that specializes in providing (e.g., offering, renting, selling)IaaS. An entity might also opt to deploy a private cloud, becoming itsown provider of infrastructure services.

In some examples, IaaS deployment is the process of putting a newapplication, or a new version of an application, onto a preparedapplication server or the like. It may also include the process ofpreparing the server (e.g., installing libraries, daemons, etc.). Thisis often managed by the cloud provider, below the hypervisor layer(e.g., the servers, storage, network hardware, and virtualization).Thus, the customer may be responsible for handling (OS), middleware,and/or application deployment (e.g., on self-service virtual machines(e.g., that can be spun up on demand) or the like.

In some examples, IaaS provisioning may refer to acquiring computers orvirtual hosts for use, and even installing needed libraries or serviceson them. In most cases, deployment does not include provisioning, andthe provisioning may need to be performed first.

In some cases, there are two different challenges for IaaS provisioning.First, there is the initial challenge of provisioning the initial set ofinfrastructure before anything is running. Second, there is thechallenge of evolving the existing infrastructure (e.g., adding newservices, changing services, removing services, etc.) once everythinghas been provisioned. In some cases, these two challenges may beaddressed by enabling the configuration of the infrastructure to bedefined declaratively. In other words, the infrastructure (e.g., whatcomponents are needed and how they interact) can be defined by one ormore configuration files. Thus, the overall topology of theinfrastructure (e.g., what resources depend on which, and how they eachwork together) can be described declaratively. In some instances, oncethe topology is defined, a workflow can be generated that creates and/ormanages the different components described in the configuration files.

In some examples, an infrastructure may have many interconnectedelements. For example, there may be one or more virtual private clouds(VPCs) (e.g., a potentially on-demand pool of configurable and/or sharedcomputing resources), also known as a core network. In some examples,there may also be one or more security group rules provisioned to definehow the security of the network will be set up and one or more virtualmachines (VMs). Other infrastructure elements may also be provisioned,such as a load balancer, a database, or the like. As more and moreinfrastructure elements are desired and/or added, the infrastructure mayincrementally evolve.

In some instances, continuous deployment techniques may be employed toenable deployment of infrastructure code across various virtualcomputing environments. Additionally, the described techniques canenable infrastructure management within these environments. In someexamples, service teams can write code that is desired to be deployed toone or more, but often many, different production environments (e.g.,across various different geographic locations, sometimes spanning theentire world). However, in some examples, the infrastructure on whichthe code will be deployed must first be set up. In some instances, theprovisioning can be done manually, a provisioning tool may be utilizedto provision the resources, and/or deployment tools may be utilized todeploy the code once the infrastructure is provisioned.

FIG. 16 is a block diagram 1600 illustrating an example pattern of anIaaS architecture, according to at least one embodiment. Serviceoperators 1602 can be communicatively coupled to a secure host tenancy1604 that can include a virtual cloud network (VCN) 1606 and a securehost subnet 1608. In some examples, the service operators 1602 may beusing one or more client computing devices, which may be portablehandheld devices (e.g., an iPhone®, cellular telephone, an iPad®,computing tablet, a personal digital assistant (PDA)) or wearabledevices (e.g., a Google Glass® head mounted display), running softwaresuch as Microsoft Windows Mobile®, and/or a variety of mobile operatingsystems such as iOS, Windows Phone, Android, BlackBerry 8, Palm OS, andthe like, and being Internet, e-mail, short message service (SMS),Blackberry®, or other communication protocol enabled. Alternatively, theclient computing devices can be general purpose personal computersincluding, by way of example, personal computers and/or laptop computersrunning various versions of Microsoft Windows®, Apple Macintosh®, and/orLinux operating systems. The client computing devices can be workstationcomputers running any of a variety of commercially-available UNIX® orUNIX-like operating systems, including without limitation the variety ofGNU/Linux operating systems, such as for example, Google Chrome OS.Alternatively, or in addition, client computing devices may be any otherelectronic device, such as a thin-client computer, an Internet-enabledgaming system (e.g., a Microsoft Xbox gaming console with or without aKinect® gesture input device), and/or a personal messaging device,capable of communicating over a network that can access the VCN 1606and/or the Internet.

The VCN 1606 can include a local peering gateway (LPG) 1610 that can becommunicatively coupled to a secure shell (SSH) VCN 1612 via an LPG 1610contained in the SSH VCN 1612. The SSH VCN 1612 can include an SSHsubnet 1614, and the SSH VCN 1612 can be communicatively coupled to acontrol plane VCN 1616 via the LPG 1610 contained in the control planeVCN 1616. Also, the SSH VCN 1612 can be communicatively coupled to adata plane VCN 1618 via an LPG 1610. The control plane VCN 1616 and thedata plane VCN 1618 can be contained in a service tenancy 1619 that canbe owned and/or operated by the IaaS provider.

The control plane VCN 1616 can include a control plane demilitarizedzone (DMZ) tier 1620 that acts as a perimeter network (e.g., portions ofa corporate network between the corporate intranet and externalnetworks). The DMZ-based servers may have restricted responsibilitiesand help keep security breaches contained. Additionally, the DMZ tier1620 can include one or more load balancer (LB) subnet(s) 1622, acontrol plane app tier 1624 that can include app subnet(s) 1626, acontrol plane data tier 1628 that can include database (DB) subnet(s)1630 (e.g., frontend DB subnet(s) and/or backend DB subnet(s)). The LBsubnet(s) 1622 contained in the control plane DMZ tier 1620 can becommunicatively coupled to the app subnet(s) 1626 contained in thecontrol plane app tier 1624 and an Internet gateway 1634 that can becontained in the control plane VCN 1616, and the app subnet(s) 1626 canbe communicatively coupled to the DB subnet(s) 1630 contained in thecontrol plane data tier 1628 and a service gateway 1636 and a networkaddress translation (NAT) gateway 1638. The control plane VCN 1616 caninclude the service gateway 1636 and the NAT gateway 1638.

The control plane VCN 1616 can include a data plane mirror app tier 1640that can include app subnet(s) 1626. The app subnet(s) 1626 contained inthe data plane mirror app tier 1640 can include a virtual networkinterface controller (VNIC) 1642 that can execute a compute instance1644. The compute instance 1644 can communicatively couple the appsubnet(s) 1626 of the data plane mirror app tier 1640 to app subnet(s)1626 that can be contained in a data plane app tier 1646.

The data plane VCN 1618 can include the data plane app tier 1646, a dataplane DMZ tier 1648, and a data plane data tier 1650. The data plane DMZtier 1648 can include LB subnet(s) 1622 that can be communicativelycoupled to the app subnet(s) 1626 of the data plane app tier 1646 andthe Internet gateway 1634 of the data plane VCN 1618. The app subnet(s)1626 can be communicatively coupled to the service gateway 1636 of thedata plane VCN 1618 and the NAT gateway 1638 of the data plane VCN 1618.The data plane data tier 1650 can also include the DB subnet(s) 1630that can be communicatively coupled to the app subnet(s) 1626 of thedata plane app tier 1646.

The Internet gateway 1634 of the control plane VCN 1616 and of the dataplane VCN 1618 can be communicatively coupled to a metadata managementservice 1652 that can be communicatively coupled to public Internet1654. Public Internet 1654 can be communicatively coupled to the NATgateway 1638 of the control plane VCN 1616 and of the data plane VCN1618. The service gateway 1636 of the control plane VCN 1616 and of thedata plane VCN 1618 can be communicatively couple to cloud services1656.

In some examples, the service gateway 1636 of the control plane VCN 1616or of the data plane VCN 1618 can make application programming interface(API) calls to cloud services 1656 without going through public Internet1654. The API calls to cloud services 1656 from the service gateway 1636can be one-way: the service gateway 1636 can make API calls to cloudservices 1656, and cloud services 1656 can send requested data to theservice gateway 1636. But, cloud services 1656 may not initiate APIcalls to the service gateway 1636.

In some examples, the secure host tenancy 1604 can be directly connectedto the service tenancy 1619, which may be otherwise isolated. The securehost subnet 1608 can communicate with the SSH subnet 1614 through an LPG1610 that may enable two-way communication over an otherwise isolatedsystem. Connecting the secure host subnet 1608 to the SSH subnet 1614may give the secure host subnet 1608 access to other entities within theservice tenancy 1619.

The control plane VCN 1616 may allow users of the service tenancy 1619to set up or otherwise provision desired resources. Desired resourcesprovisioned in the control plane VCN 1616 may be deployed or otherwiseused in the data plane VCN 1618. In some examples, the control plane VCN1616 can be isolated from the data plane VCN 1618, and the data planemirror app tier 1640 of the control plane VCN 1616 can communicate withthe data plane app tier 1646 of the data plane VCN 1618 via VNICs 1642that can be contained in the data plane mirror app tier 1640 and thedata plane app tier 1646.

In some examples, users of the system, or customers, can make requests,for example create, read, update, or delete (CRUD) operations, throughpublic Internet 1654 that can communicate the requests to the metadatamanagement service 1652. The metadata management service 1652 cancommunicate the request to the control plane VCN 1616 through theInternet gateway 1634. The request can be received by the LB subnet(s)1622 contained in the control plane DMZ tier 1620. The LB subnet(s) 1622may determine that the request is valid, and in response to thisdetermination, the LB subnet(s) 1622 can transmit the request to appsubnet(s) 1626 contained in the control plane app tier 1624. If therequest is validated and requires a call to public Internet 1654, thecall to public Internet 1654 may be transmitted to the NAT gateway 1638that can make the call to public Internet 1654. Memory that may bedesired to be stored by the request can be stored in the DB subnet(s)1630.

In some examples, the data plane mirror app tier 1640 can facilitatedirect communication between the control plane VCN 1616 and the dataplane VCN 1618. For example, changes, updates, or other suitablemodifications to configuration may be desired to be applied to theresources contained in the data plane VCN 1618. Via a VNIC 1642, thecontrol plane VCN 1616 can directly communicate with, and can therebyexecute the changes, updates, or other suitable modifications toconfiguration to, resources contained in the data plane VCN 1618.

In some embodiments, the control plane VCN 1616 and the data plane VCN1618 can be contained in the service tenancy 1619. In this case, theuser, or the customer, of the system may not own or operate either thecontrol plane VCN 1616 or the data plane VCN 1618. Instead, the IaaSprovider may own or operate the control plane VCN 1616 and the dataplane VCN 1618, both of which may be contained in the service tenancy1619. This embodiment can enable isolation of networks that may preventusers or customers from interacting with other users', or othercustomers', resources. Also, this embodiment may allow users orcustomers of the system to store databases privately without needing torely on public Internet 1654, which may not have a desired level ofsecurity, for storage.

In other embodiments, the LB subnet(s) 1622 contained in the controlplane VCN 1616 can be configured to receive a signal from the servicegateway 1636. In this embodiment, the control plane VCN 1616 and thedata plane VCN 1618 may be configured to be called by a customer of theIaaS provider without calling public Internet 1654. Customers of theIaaS provider may desire this embodiment since database(s) that thecustomers use may be controlled by the IaaS provider and may be storedon the service tenancy 1619, which may be isolated from public Internet1654.

FIG. 17 is a block diagram 1700 illustrating another example pattern ofan IaaS architecture, according to at least one embodiment. Serviceoperators 1702 (e.g. service operators 1602 of FIG. 16 ) can becommunicatively coupled to a secure host tenancy 1704 (e.g. the securehost tenancy 1604 of FIG. 16 ) that can include a virtual cloud network(VCN) 1706 (e.g. the VCN 1606 of FIG. 16 ) and a secure host subnet 1708(e.g. the secure host subnet 1608 of FIG. 16 ). The VCN 1706 can includea local peering gateway (LPG) 1710 (e.g. the LPG 1610 of FIG. 16 ) thatcan be communicatively coupled to a secure shell (SSH) VCN 1712 (e.g.the SSH VCN 1612 of FIG. 16 ) via an LPG 1610 contained in the SSH VCN1712. The SSH VCN 1712 can include an SSH subnet 1714 (e.g. the SSHsubnet 1614 of FIG. 16 ), and the SSH VCN 1712 can be communicativelycoupled to a control plane VCN 1716 (e.g. the control plane VCN 1616 ofFIG. 16 ) via an LPG 1710 contained in the control plane VCN 1716. Thecontrol plane VCN 1716 can be contained in a service tenancy 1719 (e.g.the service tenancy 1619 of FIG. 16 ), and the data plane VCN 1718 (e.g.the data plane VCN 1618 of FIG. 16 ) can be contained in a customertenancy 1721 that may be owned or operated by users, or customers, ofthe system.

The control plane VCN 1716 can include a control plane DMZ tier 1720(e.g. the control plane DMZ tier 1620 of FIG. 16 ) that can include LBsubnet(s) 1722 (e.g. LB subnet(s) 1622 of FIG. 16 ), a control plane apptier 1724 (e.g. the control plane app tier 1624 of FIG. 16 ) that caninclude app subnet(s) 1726 (e.g. app subnet(s) 1626 of FIG. 16 ), acontrol plane data tier 1728 (e.g. the control plane data tier 1628 ofFIG. 16 ) that can include database (DB) subnet(s) 1730 (e.g. similar toDB subnet(s) 1630 of FIG. 16 ). The LB subnet(s) 1722 contained in thecontrol plane DMZ tier 1720 can be communicatively coupled to the appsubnet(s) 1726 contained in the control plane app tier 1724 and anInternet gateway 1734 (e.g. the Internet gateway 1634 of FIG. 16 ) thatcan be contained in the control plane VCN 1716, and the app subnet(s)1726 can be communicatively coupled to the DB subnet(s) 1730 containedin the control plane data tier 1728 and a service gateway 1736 (e.g. theservice gateway of FIG. 16 ) and a network address translation (NAT)gateway 1738 (e.g. the NAT gateway 1638 of FIG. 16 ). The control planeVCN 1716 can include the service gateway 1736 and the NAT gateway 1738.

The control plane VCN 1716 can include a data plane mirror app tier 1740(e.g. the data plane mirror app tier 1640 of FIG. 16 ) that can includeapp subnet(s) 1726. The app subnet(s) 1726 contained in the data planemirror app tier 1740 can include a virtual network interface controller(VNIC) 1742 (e.g. the VNIC of 1642) that can execute a compute instance1744 (e.g. similar to the compute instance 1644 of FIG. 16 ). Thecompute instance 1744 can facilitate communication between the appsubnet(s) 1726 of the data plane mirror app tier 1740 and the appsubnet(s) 1726 that can be contained in a data plane app tier 1746 (e.g.the data plane app tier 1646 of FIG. 16 ) via the VNIC 1742 contained inthe data plane mirror app tier 1740 and the VNIC 1742 contained in thedata plane app tier 1746.

The Internet gateway 1734 contained in the control plane VCN 1716 can becommunicatively coupled to a metadata management service 1752 (e.g. themetadata management service 1652 of FIG. 16 ) that can becommunicatively coupled to public Internet 1754 (e.g. public Internet1654 of FIG. 16 ). Public Internet 1754 can be communicatively coupledto the NAT gateway 1738 contained in the control plane VCN 1716. Theservice gateway 1736 contained in the control plane VCN 1716 can becommunicatively couple to cloud services 1756 (e.g. cloud services 1656of FIG. 16 ).

In some examples, the data plane VCN 1718 can be contained in thecustomer tenancy 1721. In this case, the IaaS provider may provide thecontrol plane VCN 1716 for each customer, and the IaaS provider may, foreach customer, set up a unique compute instance 1744 that is containedin the service tenancy 1719. Each compute instance 1744 may allowcommunication between the control plane VCN 1716, contained in theservice tenancy 1719, and the data plane VCN 1718 that is contained inthe customer tenancy 1721. The compute instance 1744 may allowresources, that are provisioned in the control plane VCN 1716 that iscontained in the service tenancy 1719, to be deployed or otherwise usedin the data plane VCN 1718 that is contained in the customer tenancy1721.

In other examples, the customer of the IaaS provider may have databasesthat live in the customer tenancy 1721. In this example, the controlplane VCN 1716 can include the data plane mirror app tier 1740 that caninclude app subnet(s) 1726. The data plane mirror app tier 1740 canreside in the data plane VCN 1718, but the data plane mirror app tier1740 may not live in the data plane VCN 1718. That is, the data planemirror app tier 1740 may have access to the customer tenancy 1721, butthe data plane mirror app tier 1740 may not exist in the data plane VCN1718 or be owned or operated by the customer of the IaaS provider. Thedata plane mirror app tier 1740 may be configured to make calls to thedata plane VCN 1718 but may not be configured to make calls to anyentity contained in the control plane VCN 1716. The customer may desireto deploy or otherwise use resources in the data plane VCN 1718 that areprovisioned in the control plane VCN 1716, and the data plane mirror apptier 1740 can facilitate the desired deployment, or other usage ofresources, of the customer.

In some embodiments, the customer of the IaaS provider can apply filtersto the data plane VCN 1718. In this embodiment, the customer candetermine what the data plane VCN 1718 can access, and the customer mayrestrict access to public Internet 1754 from the data plane VCN 1718.The IaaS provider may not be able to apply filters or otherwise controlaccess of the data plane VCN 1718 to any outside networks or databases.Applying filters and controls by the customer onto the data plane VCN1718, contained in the customer tenancy 1721, can help isolate the dataplane VCN 1718 from other customers and from public Internet 1754.

In some embodiments, cloud services 1756 can be called by the servicegateway 1736 to access services that may not exist on public Internet1754, on the control plane VCN 1716, or on the data plane VCN 1718. Theconnection between cloud services 1756 and the control plane VCN 1716 orthe data plane VCN 1718 may not be live or continuous. Cloud services1756 may exist on a different network owned or operated by the IaaSprovider. Cloud services 1756 may be configured to receive calls fromthe service gateway 1736 and may be configured to not receive calls frompublic Internet 1754. Some cloud services 1756 may be isolated fromother cloud services 1756, and the control plane VCN 1716 may beisolated from cloud services 1756 that may not be in the same region asthe control plane VCN 1716. For example, the control plane VCN 1716 maybe located in “Region 1,” and cloud service “Deployment 16,” may belocated in Region 1 and in “Region 2.” If a call to Deployment 16 ismade by the service gateway 1736 contained in the control plane VCN 1716located in Region 1, the call may be transmitted to Deployment 16 inRegion 1. In this example, the control plane VCN 1716, or Deployment 16in Region 1, may not be communicatively coupled to, or otherwise incommunication with, Deployment 16 in Region 2.

FIG. 18 is a block diagram 1800 illustrating another example pattern ofan IaaS architecture, according to at least one embodiment. Serviceoperators 1802 (e.g. service operators 1602 of FIG. 16 ) can becommunicatively coupled to a secure host tenancy 1804 (e.g. the securehost tenancy 1604 of FIG. 16 ) that can include a virtual cloud network(VCN) 1806 (e.g. the VCN 1606 of FIG. 16 ) and a secure host subnet 1808(e.g. the secure host subnet 1608 of FIG. 16 ). The VCN 1806 can includean LPG 1810 (e.g. the LPG 1610 of FIG. 16 ) that can be communicativelycoupled to an SSH VCN 1812 (e.g. the SSH VCN 1612 of FIG. 16 ) via anLPG 1810 contained in the SSH VCN 1812. The SSH VCN 1812 can include anSSH subnet 1814 (e.g. the SSH subnet 1614 of FIG. 16 ), and the SSH VCN1812 can be communicatively coupled to a control plane VCN 1816 (e.g.the control plane VCN 1616 of FIG. 16 ) via an LPG 1810 contained in thecontrol plane VCN 1816 and to a data plane VCN 1818 (e.g. the data plane1618 of FIG. 16 ) via an LPG 1810 contained in the data plane VCN 1818.The control plane VCN 1816 and the data plane VCN 1818 can be containedin a service tenancy 1819 (e.g. the service tenancy 1619 of FIG. 16 ).

The control plane VCN 1816 can include a control plane DMZ tier 1820(e.g. the control plane DMZ tier 1620 of FIG. 16 ) that can include loadbalancer (LB) subnet(s) 1822 (e.g. LB subnet(s) 1622 of FIG. 16 ), acontrol plane app tier 1824 (e.g. the control plane app tier 1624 ofFIG. 16 ) that can include app subnet(s) 1826 (e.g. similar to appsubnet(s) 1626 of FIG. 16 ), a control plane data tier 1828 (e.g. thecontrol plane data tier 1628 of FIG. 16 ) that can include DB subnet(s)1830. The LB subnet(s) 1822 contained in the control plane DMZ tier 1820can be communicatively coupled to the app subnet(s) 1826 contained inthe control plane app tier 1824 and to an Internet gateway 1834 (e.g.the Internet gateway 1634 of FIG. 16 ) that can be contained in thecontrol plane VCN 1816, and the app subnet(s) 1826 can becommunicatively coupled to the DB subnet(s) 1830 contained in thecontrol plane data tier 1828 and to a service gateway 1836 (e.g. theservice gateway of FIG. 16 ) and a network address translation (NAT)gateway 1838 (e.g. the NAT gateway 1638 of FIG. 16 ). The control planeVCN 1816 can include the service gateway 1836 and the NAT gateway 1838.

The data plane VCN 1818 can include a data plane app tier 1846 (e.g. thedata plane app tier 1646 of FIG. 16 ), a data plane DMZ tier 1848 (e.g.the data plane DMZ tier 1648 of FIG. 16 ), and a data plane data tier1850 (e.g. the data plane data tier 1650 of FIG. 16 ). The data planeDMZ tier 1848 can include LB subnet(s) 1822 that can be communicativelycoupled to trusted app subnet(s) 1860 and untrusted app subnet(s) 1862of the data plane app tier 1846 and the Internet gateway 1834 containedin the data plane VCN 1818. The trusted app subnet(s) 1860 can becommunicatively coupled to the service gateway 1836 contained in thedata plane VCN 1818, the NAT gateway 1838 contained in the data planeVCN 1818, and DB subnet(s) 1830 contained in the data plane data tier1850. The untrusted app subnet(s) 1862 can be communicatively coupled tothe service gateway 1836 contained in the data plane VCN 1818 and DBsubnet(s) 1830 contained in the data plane data tier 1850. The dataplane data tier 1850 can include DB subnet(s) 1830 that can becommunicatively coupled to the service gateway 1836 contained in thedata plane VCN 1818.

The untrusted app subnet(s) 1862 can include one or more primary VNICs1864(1)-(N) that can be communicatively coupled to tenant virtualmachines (VMs) 1866(1)-(N). Each tenant VM 1866(1)-(N) can becommunicatively coupled to a respective app subnet 1867(1)-(N) that canbe contained in respective container egress VCNs 1868(1)-(N) that can becontained in respective customer tenancies 1870(1)-(N). Respectivesecondary VNICs 1872(1)-(N) can facilitate communication between theuntrusted app subnet(s) 1862 contained in the data plane VCN 1818 andthe app subnet contained in the container egress VCNs 1868(1)-(N). Eachcontainer egress VCNs 1868(1)-(N) can include a NAT gateway 1838 thatcan be communicatively coupled to public Internet 1854 (e.g. publicInternet 1654 of FIG. 16 ).

The Internet gateway 1834 contained in the control plane VCN 1816 andcontained in the data plane VCN 1818 can be communicatively coupled to ametadata management service 1852 (e.g. the metadata management system1652 of FIG. 16 ) that can be communicatively coupled to public Internet1854. Public Internet 1854 can be communicatively coupled to the NATgateway 1838 contained in the control plane VCN 1816 and contained inthe data plane VCN 1818. The service gateway 1836 contained in thecontrol plane VCN 1816 and contained in the data plane VCN 1818 can becommunicatively couple to cloud services 1856.

In some embodiments, the data plane VCN 1818 can be integrated withcustomer tenancies 1870. This integration can be useful or desirable forcustomers of the IaaS provider in some cases such as a case that maydesire support when executing code. The customer may provide code to runthat may be destructive, may communicate with other customer resources,or may otherwise cause undesirable effects. In response to this, theIaaS provider may determine whether to run code given to the IaaSprovider by the customer.

In some examples, the customer of the IaaS provider may grant temporarynetwork access to the IaaS provider and request a function to beattached to the data plane tier app 1846. Code to run the function maybe executed in the VMs 1866(1)-(N), and the code may not be configuredto run anywhere else on the data plane VCN 1818. Each VM 1866(1)-(N) maybe connected to one customer tenancy 1870. Respective containers1871(1)-(N) contained in the VMs 1866(1)-(N) may be configured to runthe code. In this case, there can be a dual isolation (e.g., thecontainers 1871(1)-(N) running code, where the containers 1871(1)-(N)may be contained in at least the VM 1866(1)-(N) that are contained inthe untrusted app subnet(s) 1862), which may help prevent incorrect orotherwise undesirable code from damaging the network of the IaaSprovider or from damaging a network of a different customer. Thecontainers 1871(1)-(N) may be communicatively coupled to the customertenancy 1870 and may be configured to transmit or receive data from thecustomer tenancy 1870. The containers 1871(1)-(N) may not be configuredto transmit or receive data from any other entity in the data plane VCN1818. Upon completion of running the code, the IaaS provider may kill orotherwise dispose of the containers 1871(1)-(N).

In some embodiments, the trusted app subnet(s) 1860 may run code thatmay be owned or operated by the IaaS provider. In this embodiment, thetrusted app subnet(s) 1860 may be communicatively coupled to the DBsubnet(s) 1830 and be configured to execute CRUD operations in the DBsubnet(s) 1830. The untrusted app subnet(s) 1862 may be communicativelycoupled to the DB subnet(s) 1830, but in this embodiment, the untrustedapp subnet(s) may be configured to execute read operations in the DBsubnet(s) 1830. The containers 1871(1)-(N) that can be contained in theVM 1866(1)-(N) of each customer and that may run code from the customermay not be communicatively coupled with the DB subnet(s) 1830.

In other embodiments, the control plane VCN 1816 and the data plane VCN1818 may not be directly communicatively coupled. In this embodiment,there may be no direct communication between the control plane VCN 1816and the data plane VCN 1818. However, communication can occur indirectlythrough at least one method. An LPG 1810 may be established by the IaaSprovider that can facilitate communication between the control plane VCN1816 and the data plane VCN 1818. In another example, the control planeVCN 1816 or the data plane VCN 1818 can make a call to cloud services1856 via the service gateway 1836. For example, a call to cloud services1856 from the control plane VCN 1816 can include a request for a servicethat can communicate with the data plane VCN 1818.

FIG. 19 is a block diagram 1900 illustrating another example pattern ofan IaaS architecture, according to at least one embodiment. Serviceoperators 1902 (e.g. service operators 1602 of FIG. 16 ) can becommunicatively coupled to a secure host tenancy 1904 (e.g. the securehost tenancy 1604 of FIG. 16 ) that can include a virtual cloud network(VCN) 1906 (e.g. the VCN 1606 of FIG. 16 ) and a secure host subnet 1908(e.g. the secure host subnet 1608 of FIG. 16 ). The VCN 1906 can includean LPG 1910 (e.g. the LPG 1610 of FIG. 16 ) that can be communicativelycoupled to an SSH VCN 1912 (e.g. the SSH VCN 1612 of FIG. 16 ) via anLPG 1910 contained in the SSH VCN 1912. The SSH VCN 1912 can include anSSH subnet 1914 (e.g. the SSH subnet 1614 of FIG. 16 ), and the SSH VCN1912 can be communicatively coupled to a control plane VCN 1916 (e.g.the control plane VCN 1616 of FIG. 16 ) via an LPG 1910 contained in thecontrol plane VCN 1916 and to a data plane VCN 1918 (e.g. the data plane1618 of FIG. 16 ) via an LPG 1910 contained in the data plane VCN 1918.The control plane VCN 1916 and the data plane VCN 1918 can be containedin a service tenancy 1919 (e.g. the service tenancy 1619 of FIG. 16 ).

The control plane VCN 1916 can include a control plane DMZ tier 1920(e.g. the control plane DMZ tier 1620 of FIG. 16 ) that can include LBsubnet(s) 1922 (e.g. LB subnet(s) 1622 of FIG. 16 ), a control plane apptier 1924 (e.g. the control plane app tier 1624 of FIG. 16 ) that caninclude app subnet(s) 1926 (e.g. app subnet(s) 1626 of FIG. 16 ), acontrol plane data tier 1928 (e.g. the control plane data tier 1628 ofFIG. 16 ) that can include DB subnet(s) 1930 (e.g. DB subnet(s) 1830 ofFIG. 18 ). The LB subnet(s) 1922 contained in the control plane DMZ tier1920 can be communicatively coupled to the app subnet(s) 1926 containedin the control plane app tier 1924 and to an Internet gateway 1934 (e.g.the Internet gateway 1634 of FIG. 16 ) that can be contained in thecontrol plane VCN 1916, and the app subnet(s) 1926 can becommunicatively coupled to the DB subnet(s) 1930 contained in thecontrol plane data tier 1928 and to a service gateway 1936 (e.g. theservice gateway of FIG. 16 ) and a network address translation (NAT)gateway 1938 (e.g. the NAT gateway 1638 of FIG. 16 ). The control planeVCN 1916 can include the service gateway 1936 and the NAT gateway 1938.

The data plane VCN 1918 can include a data plane app tier 1946 (e.g. thedata plane app tier 1646 of FIG. 16 ), a data plane DMZ tier 1948 (e.g.the data plane DMZ tier 1648 of FIG. 16 ), and a data plane data tier1950 (e.g. the data plane data tier 1650 of FIG. 16 ). The data planeDMZ tier 1948 can include LB subnet(s) 1922 that can be communicativelycoupled to trusted app subnet(s) 1960 (e.g. trusted app subnet(s) 1860of FIG. 18 ) and untrusted app subnet(s) 1962 (e.g. untrusted appsubnet(s) 1862 of FIG. 18 ) of the data plane app tier 1946 and theInternet gateway 1934 contained in the data plane VCN 1918. The trustedapp subnet(s) 1960 can be communicatively coupled to the service gateway1936 contained in the data plane VCN 1918, the NAT gateway 1938contained in the data plane VCN 1918, and DB subnet(s) 1930 contained inthe data plane data tier 1950. The untrusted app subnet(s) 1962 can becommunicatively coupled to the service gateway 1936 contained in thedata plane VCN 1918 and DB subnet(s) 1930 contained in the data planedata tier 1950. The data plane data tier 1950 can include DB subnet(s)1930 that can be communicatively coupled to the service gateway 1936contained in the data plane VCN 1918.

The untrusted app subnet(s) 1962 can include primary VNICs 1964(1)-(N)that can be communicatively coupled to tenant virtual machines (VMs)1966(1)-(N) residing within the untrusted app subnet(s) 1962. Eachtenant VM 1966(1)-(N) can run code in a respective container1967(1)-(N), and be communicatively coupled to an app subnet 1926 thatcan be contained in a data plane app tier 1946 that can be contained ina container egress VCN 1968. Respective secondary VNICs 1972(1)-(N) canfacilitate communication between the untrusted app subnet(s) 1962contained in the data plane VCN 1918 and the app subnet contained in thecontainer egress VCN 1968. The container egress VCN can include a NATgateway 1938 that can be communicatively coupled to public Internet 1954(e.g. public Internet 1654 of FIG. 16 ).

The Internet gateway 1934 contained in the control plane VCN 1916 andcontained in the data plane VCN 1918 can be communicatively coupled to ametadata management service 1952 (e.g. the metadata management system1652 of FIG. 16 ) that can be communicatively coupled to public Internet1954. Public Internet 1954 can be communicatively coupled to the NATgateway 1938 contained in the control plane VCN 1916 and contained inthe data plane VCN 1918. The service gateway 1936 contained in thecontrol plane VCN 1916 and contained in the data plane VCN 1918 can becommunicatively couple to cloud services 1956.

In some examples, the pattern illustrated by the architecture of blockdiagram 1900 of FIG. 19 may be considered an exception to the patternillustrated by the architecture of block diagram 1800 of FIG. 18 and maybe desirable for a customer of the IaaS provider if the IaaS providercannot directly communicate with the customer (e.g., a disconnectedregion). The respective containers 1967(1)-(N) that are contained in theVMs 1966(1)-(N) for each customer can be accessed in real-time by thecustomer. The containers 1967(1)-(N) may be configured to make calls torespective secondary VNICs 1972(1)-(N) contained in app subnet(s) 1926of the data plane app tier 1946 that can be contained in the containeregress VCN 1968. The secondary VNICs 1972(1)-(N) can transmit the callsto the NAT gateway 1938 that may transmit the calls to public Internet1954. In this example, the containers 1967(1)-(N) that can be accessedin real-time by the customer can be isolated from the control plane VCN1916 and can be isolated from other entities contained in the data planeVCN 1918. The containers 1967(1)-(N) may also be isolated from resourcesfrom other customers.

In other examples, the customer can use the containers 1967(1)-(N) tocall cloud services 1956. In this example, the customer may run code inthe containers 1967(1)-(N) that requests a service from cloud services1956. The containers 1967(1)-(N) can transmit this request to thesecondary VNICs 1972(1)-(N) that can transmit the request to the NATgateway that can transmit the request to public Internet 1954. PublicInternet 1954 can transmit the request to LB subnet(s) 1922 contained inthe control plane VCN 1916 via the Internet gateway 1934. In response todetermining the request is valid, the LB subnet(s) can transmit therequest to app subnet(s) 1926 that can transmit the request to cloudservices 1956 via the service gateway 1936.

It should be appreciated that IaaS architectures 1600, 1700, 1800, 1900depicted in the figures may have other components than those depicted.Further, the embodiments shown in the figures are only some examples ofa cloud infrastructure system that may incorporate an embodiment of thedisclosure. In some other embodiments, the IaaS systems may have more orfewer components than shown in the figures, may combine two or morecomponents, or may have a different configuration or arrangement ofcomponents.

In certain embodiments, the IaaS systems described herein may include asuite of applications, middleware, and database service offerings thatare delivered to a customer in a self-service, subscription-based,elastically scalable, reliable, highly available, and secure manner. Anexample of such an IaaS system is the Oracle Cloud Infrastructure (OCI)provided by the present assignee.

FIG. 20 illustrates an example computer system 2000, in which variousembodiments may be implemented. The system 2000 may be used to implementany of the computer systems described above. As shown in the figure,computer system 2000 includes a processing unit 2004 that communicateswith a number of peripheral subsystems via a bus subsystem 2002. Theseperipheral subsystems may include a processing acceleration unit 2006,an I/O subsystem 2008, a storage subsystem 2018 and a communicationssubsystem 2024. Storage subsystem 2018 includes tangiblecomputer-readable storage media 2022 and a system memory 2010.

Bus subsystem 2002 provides a mechanism for letting the variouscomponents and subsystems of computer system 2000 communicate with eachother as intended. Although bus subsystem 2002 is shown schematically asa single bus, alternative embodiments of the bus subsystem may utilizemultiple buses. Bus subsystem 2002 may be any of several types of busstructures including a memory bus or memory controller, a peripheralbus, and a local bus using any of a variety of bus architectures. Forexample, such architectures may include an Industry StandardArchitecture (ISA) bus, Micro Channel Architecture (MCA) bus, EnhancedISA (EISA) bus, Video Electronics Standards Association (VESA) localbus, and Peripheral Component Interconnect (PCI) bus, which can beimplemented as a Mezzanine bus manufactured to the IEEE P1386.1standard.

Processing unit 2004, which can be implemented as one or more integratedcircuits (e.g., a conventional microprocessor or microcontroller),controls the operation of computer system 2000. One or more processorsmay be included in processing unit 2004. These processors may includesingle core or multicore processors. In certain embodiments, processingunit 2004 may be implemented as one or more independent processing units2032 and/or 2034 with single or multicore processors included in eachprocessing unit. In other embodiments, processing unit 2004 may also beimplemented as a quad-core processing unit formed by integrating twodual-core processors into a single chip.

In various embodiments, processing unit 2004 can execute a variety ofprograms in response to program code and can maintain multipleconcurrently executing programs or processes. At any given time, some orall of the program code to be executed can be resident in processor(s)2004 and/or in storage subsystem 2018. Through suitable programming,processor(s) 2004 can provide various functionalities described above.Computer system 2000 may additionally include a processing accelerationunit 2006, which can include a digital signal processor (DSP), aspecial-purpose processor, and/or the like.

I/O subsystem 2008 may include user interface input devices and userinterface output devices. User interface input devices may include akeyboard, pointing devices such as a mouse or trackball, a touchpad ortouch screen incorporated into a display, a scroll wheel, a click wheel,a dial, a button, a switch, a keypad, audio input devices with voicecommand recognition systems, microphones, and other types of inputdevices. User interface input devices may include, for example, motionsensing and/or gesture recognition devices such as the Microsoft Kinect®motion sensor that enables users to control and interact with an inputdevice, such as the Microsoft Xbox® 360 game controller, through anatural user interface using gestures and spoken commands. Userinterface input devices may also include eye gesture recognition devicessuch as the Google Glass® blink detector that detects eye activity(e.g., ‘blinking’ while taking pictures and/or making a menu selection)from users and transforms the eye gestures as input into an input device(e.g., Google Glass®). Additionally, user interface input devices mayinclude voice recognition sensing devices that enable users to interactwith voice recognition systems (e.g., Siri® navigator), through voicecommands.

User interface input devices may also include, without limitation, threedimensional (3D) mice, joysticks or pointing sticks, gamepads andgraphic tablets, and audio/visual devices such as speakers, digitalcameras, digital camcorders, portable media players, webcams, imagescanners, fingerprint scanners, barcode reader 3D scanners, 3D printers,laser rangefinders, and eye gaze tracking devices. Additionally, userinterface input devices may include, for example, medical imaging inputdevices such as computed tomography, magnetic resonance imaging,position emission tomography, medical ultrasonography devices. Userinterface input devices may also include, for example, audio inputdevices such as MIDI keyboards, digital musical instruments and thelike.

User interface output devices may include a display subsystem, indicatorlights, or non-visual displays such as audio output devices, etc. Thedisplay subsystem may be a cathode ray tube (CRT), a flat-panel device,such as that using a liquid crystal display (LCD) or plasma display, aprojection device, a touch screen, and the like. In general, use of theterm “output device” is intended to include all possible types ofdevices and mechanisms for outputting information from computer system2000 to a user or other computer. For example, user interface outputdevices may include, without limitation, a variety of display devicesthat visually convey text, graphics and audio/video information such asmonitors, printers, speakers, headphones, automotive navigation systems,plotters, voice output devices, and modems.

Computer system 2000 may comprise a storage subsystem 2018 thatcomprises software elements, shown as being currently located within asystem memory 2010. System memory 2010 may store program instructionsthat are loadable and executable on processing unit 2004, as well asdata generated during the execution of these programs.

Depending on the configuration and type of computer system 2000, systemmemory 2010 may be volatile (such as random access memory (RAM)) and/ornon-volatile (such as read-only memory (ROM), flash memory, etc.) TheRAM typically contains data and/or program modules that are immediatelyaccessible to and/or presently being operated and executed by processingunit 2004. In some implementations, system memory 2010 may includemultiple different types of memory, such as static random access memory(SRAM) or dynamic random access memory (DRAM). In some implementations,a basic input/output system (BIOS), containing the basic routines thathelp to transfer information between elements within computer system2000, such as during start-up, may typically be stored in the ROM. Byway of example, and not limitation, system memory 2010 also illustratesapplication programs 2012, which may include client applications, Webbrowsers, mid-tier applications, relational database management systems(RDBMS), etc., program data 2014, and an operating system 2016. By wayof example, operating system 2016 may include various versions ofMicrosoft Windows®, Apple Macintosh®, and/or Linux operating systems, avariety of commercially-available UNIX® or UNIX-like operating systems(including without limitation the variety of GNU/Linux operatingsystems, the Google Chrome® OS, and the like) and/or mobile operatingsystems such as iOS, Windows® Phone, Android® OS, BlackBerry® 20 OS, andPalm® OS operating systems.

Storage subsystem 2018 may also provide a tangible computer-readablestorage medium for storing the basic programming and data constructsthat provide the functionality of some embodiments. Software (programs,code modules, instructions) that when executed by a processor providethe functionality described above may be stored in storage subsystem2018. These software modules or instructions may be executed byprocessing unit 2004. Storage subsystem 2018 may also provide arepository for storing data used in accordance with the presentdisclosure.

Storage subsystem 2000 may also include a computer-readable storagemedia reader 2020 that can further be connected to computer-readablestorage media 2022. Together and, optionally, in combination with systemmemory 2010, computer-readable storage media 2022 may comprehensivelyrepresent remote, local, fixed, and/or removable storage devices plusstorage media for temporarily and/or more permanently containing,storing, transmitting, and retrieving computer-readable information.

Computer-readable storage media 2022 containing code, or portions ofcode, can also include any appropriate media known or used in the art,including storage media and communication media, such as but not limitedto, volatile and non-volatile, removable and non-removable mediaimplemented in any method or technology for storage and/or transmissionof information. This can include tangible computer-readable storagemedia such as RAM, ROM, electronically erasable programmable ROM(EEPROM), flash memory or other memory technology, CD-ROM, digitalversatile disk (DVD), or other optical storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or other tangible computer readable media. This can also includenontangible computer-readable media, such as data signals, datatransmissions, or any other medium which can be used to transmit thedesired information and which can be accessed by computing system 2000.

By way of example, computer-readable storage media 2022 may include ahard disk drive that reads from or writes to non-removable, nonvolatilemagnetic media, a magnetic disk drive that reads from or writes to aremovable, nonvolatile magnetic disk, and an optical disk drive thatreads from or writes to a removable, nonvolatile optical disk such as aCD ROM, DVD, and Blu-Ray® disk, or other optical media.Computer-readable storage media 2022 may include, but is not limited to,Zip® drives, flash memory cards, universal serial bus (USB) flashdrives, secure digital (SD) cards, DVD disks, digital video tape, andthe like. Computer-readable storage media 2022 may also include,solid-state drives (SSD) based on non-volatile memory such asflash-memory based SSDs, enterprise flash drives, solid state ROM, andthe like, SSDs based on volatile memory such as solid state RAM, dynamicRAM, static RAM, DRAM-based SSDs, magnetoresistive RAM (MRAM) SSDs, andhybrid SSDs that use a combination of DRAM and flash memory based SSDs.The disk drives and their associated computer-readable media may providenon-volatile storage of computer-readable instructions, data structures,program modules, and other data for computer system 2000.

Communications subsystem 2024 provides an interface to other computersystems and networks. Communications subsystem 2024 serves as aninterface for receiving data from and transmitting data to other systemsfrom computer system 2000. For example, communications subsystem 2024may enable computer system 2000 to connect to one or more devices viathe Internet. In some embodiments communications subsystem 2024 caninclude radio frequency (RF) transceiver components for accessingwireless voice and/or data networks (e.g., using cellular telephonetechnology, advanced data network technology, such as 3G, 4G or EDGE(enhanced data rates for global evolution), WiFi (IEEE 802.11 familystandards, or other mobile communication technologies, or anycombination thereof), global positioning system (GPS) receivercomponents, and/or other components. In some embodiments communicationssubsystem 2024 can provide wired network connectivity (e.g., Ethernet)in addition to or instead of a wireless interface.

In some embodiments, communications subsystem 2024 may also receiveinput communication in the form of structured and/or unstructured datafeeds 2026, event streams 2028, event updates 2030, and the like onbehalf of one or more users who may use computer system 2000.

By way of example, communications subsystem 2024 may be configured toreceive data feeds 2026 in real-time from users of social networksand/or other communication services such as Twitter® feeds, Facebook®updates, web feeds such as Rich Site Summary (RSS) feeds, and/orreal-time updates from one or more third party information sources.

Additionally, communications subsystem 2024 may also be configured toreceive data in the form of continuous data streams, which may includeevent streams 2028 of real-time events and/or event updates 2030, thatmay be continuous or unbounded in nature with no explicit end. Examplesof applications that generate continuous data may include, for example,sensor data applications, financial tickers, network performancemeasuring tools (e.g. network monitoring and traffic managementapplications), clickstream analysis tools, automobile trafficmonitoring, and the like.

Communications subsystem 2024 may also be configured to output thestructured and/or unstructured data feeds 2026, event streams 2028,event updates 2030, and the like to one or more databases that may be incommunication with one or more streaming data source computers coupledto computer system 2000.

Computer system 2000 can be one of various types, including a handheldportable device (e.g., an iPhone® cellular phone, an iPad® computingtablet, a PDA), a wearable device (e.g., a Google Glass® head mounteddisplay), a PC, a workstation, a mainframe, a kiosk, a server rack, orany other data processing system.

In the foregoing description, for the purposes of explanation, specificdetails are set forth to provide a thorough understanding of examples ofthe disclosure. However, it will be apparent that various examples maybe practiced without these specific details. The ensuing descriptionprovides examples only and is not intended to limit the scope,applicability, or configuration of the disclosure. Rather, the ensuingdescription of the examples will provide those skilled in the art withan enabling description for implementing an example. It should beunderstood that various changes may be made in the function andarrangement of elements without departing from the spirit and scope ofthe disclosure as set forth in the appended claims. The figures anddescription are not intended to be restrictive. Circuits, systems,networks, processes, and other components may be shown as components inblock diagram form in order not to obscure the examples in unnecessarydetail. In other instances, well-known circuits, processes, algorithms,structures, and techniques may be shown without unnecessary detail inorder to avoid obscuring the examples. The teachings disclosed hereincan also be applied to various types of applications such as mobileapplications, non-mobile applications, desktop applications, webapplications, enterprise applications, and the like. Further, theteachings of this disclosure are not restricted to a particularoperating environment (e.g., operating systems, devices, platforms, andthe like), but instead can be applied to multiple different operatingenvironments.

Also, it is noted that individual examples may be described as a processwhich is depicted as a flowchart, a flow diagram, a data flow diagram, astructure diagram, or a block diagram. Although a flowchart may describethe operations as a sequential process, many of the operations may beperformed in parallel or concurrently. In addition, the order of theoperations may be rearranged. A process is terminated when itsoperations are completed, but the process could have additional stepsnot included in a figure. A process may correspond to a method, afunction, a procedure, a subroutine, a subprogram, and so on. When aprocess corresponds to a function, its termination may correspond to areturn of the function to the calling function or the main function.

The word “example” and “exemplary” is used herein to mean “serving as anexample, instance, or illustration.” Any embodiment or design describedherein as “exemplary” or “example” is not necessarily to be construed aspreferred or advantageous over other embodiments or designs.

The term “machine-readable storage medium” or “computer-readable storagemedium” includes, but is not limited to, portable or non-portablestorage devices, optical storage devices, and various other mediumscapable of storing, containing, or carrying instruction(s) and/or data.A machine-readable storage medium or computer-readable storage mediummay include a non-transitory medium in which data may be stored andwhich does not include carrier waves and/or transitory electronicsignals propagating wirelessly or over wired connections. Examples of anon-transitory medium may include, but are not limited to, a magneticdisk or tape, optical storage media such as compact disk (CD) or digitalversatile disk (DVD), flash memory, or memory or memory devices. Acomputer-program product may include code and/or machine-executableinstructions that may represent a procedure, a function, a subprogram, aprogram, a routine, a subroutine, a module, a software package, a class,or any combination of instructions, data structures, or programstatements. A code segment may be coupled to another code segment or ahardware circuit by passing and/or receiving information, data,arguments, parameters, or memory contents. Information, arguments,parameters, data, and so forth may be passed, forwarded, or transmittedvia any suitable means including memory sharing, message passing, tokenpassing, network transmission, and so forth.

Furthermore, examples may be implemented by hardware, software,firmware, middleware, microcode, hardware description languages, or anycombination thereof. When implemented in software, firmware, middleware,or microcode, the program code or code segments to perform the necessarytasks (e.g., a computer-program product) may be stored in amachine-readable medium. A processor(s) may perform the necessary tasks.Systems depicted in some of the figures may be provided in variousconfigurations. In some examples, the systems may be configured as adistributed system where one or more components of the system aredistributed across one or more networks in a cloud computing system.Where components are described as being “configured to” perform certainoperations, such configuration may be accomplished, for example, bydesigning electronic circuits or other hardware to perform theoperation, by programming or controlling electronic circuits (e.g.,microprocessors or other suitable electronic circuits) to perform theoperation, or any combination thereof.

Although specific embodiments of the disclosure have been described,various modifications, alterations, alternative constructions, andequivalents are also encompassed within the scope of the disclosure.Embodiments of the present disclosure are not restricted to operationwithin certain specific data processing environments, but are free tooperate within a plurality of data processing environments.Additionally, although embodiments of the present disclosure have beendescribed using a particular series of transactions and steps, it shouldbe apparent to those skilled in the art that the scope of the presentdisclosure is not limited to the described series of transactions andsteps. Various features and aspects of the above-described embodimentsmay be used individually or jointly.

Further, while embodiments of the present disclosure have been describedusing a particular combination of hardware and software, it should berecognized that other combinations of hardware and software are alsowithin the scope of the present disclosure. Embodiments of the presentdisclosure may be implemented only in hardware, or only in software, orusing combinations thereof. The various processes described herein canbe implemented on the same processor or different processors in anycombination. Accordingly, where components or modules are described asbeing configured to perform certain operations, such configuration canbe accomplished, e.g., by designing electronic circuits to perform theoperation, by programming programmable electronic circuits (such asmicroprocessors) to perform the operation, or any combination thereof.Processes can communicate using a variety of techniques including, butnot limited to, conventional techniques for inter process communication,and different pairs of processes may use different techniques, or thesame pair of processes may use different techniques at different times.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that additions, subtractions, deletions, and other modificationsand changes may be made thereunto without departing from the broaderspirit and scope as set forth in the claims. Thus, although specificdisclosure embodiments have been described, these are not intended to belimiting. Various modifications and equivalents are within the scope ofthe following claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the disclosed embodiments (especially in thecontext of the following claims) are to be construed to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising,” “having,” “including,”and “containing” are to be construed as open-ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. The term“connected” is to be construed as partly or wholly contained within,attached to, or joined together, even if there is something intervening.Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate embodiments of the disclosure anddoes not pose a limitation on the scope of the disclosure unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe disclosure.

Disjunctive language such as the phrase “at least one of X, Y, or Z,”unless specifically stated otherwise, is intended to be understoodwithin the context as used in general to present that an item, term,etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y,and/or Z). Thus, such disjunctive language is not generally intended to,and should not, imply that certain embodiments require at least one ofX, at least one of Y, or at least one of Z to each be present.

Preferred embodiments of this disclosure are described herein, includingthe best mode known for carrying out the disclosure. Variations of thosepreferred embodiments may become apparent to those of ordinary skill inthe art upon reading the foregoing description. Those of ordinary skillshould be able to employ such variations as appropriate and thedisclosure may be practiced otherwise than as specifically describedherein. Accordingly, this disclosure includes all modifications andequivalents of the subject matter recited in the claims appended heretoas permitted by applicable law. Moreover, any combination of theabove-described elements in all possible variations thereof isencompassed by the disclosure unless otherwise indicated herein.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

In the foregoing specification, aspects of the disclosure are describedwith reference to specific embodiments thereof, but those skilled in theart will recognize that the disclosure is not limited thereto. Variousfeatures and aspects of the above-described disclosure may be usedindividually or jointly. Further, embodiments can be utilized in anynumber of environments and applications beyond those described hereinwithout departing from the broader spirit and scope of thespecification. The specification and drawings are, accordingly, to beregarded as illustrative rather than restrictive.

What is claimed is:
 1. A network virtualization device comprising: aplurality of ports comprising a first port connected with a first hostmachine hosting a first compute instance, the first compute instancebeing a first member of a virtual Layer 2 (L2) network; one or moreprocessors; and one or more memories storing instructions, that uponexecution by the one or more processors, configure the networkvirtualization device to: generate a first L2 bridge protocol data unit(BPDU) by applying a first loop detection protocol specific, from amongthe plurality of ports, to only the first port and the first hostmachine; transmit, to the first compute instance via the first port, afirst frame that includes the first L2 BPDU; receive, from the firstcompute instance via the first port, a second frame; determine that thesecond frame comprises the first L2 BPDU; and determine that a loopexists between the network virtualization device and the first computeinstance based on the first loop detection protocol and the first L2BPDU of the second frame.
 2. The network virtualization device of claim1, wherein the execution of the instructions further configures thenetwork virtualization device to: disable the first port based on theloop; receive a third frame that comprises a MAC address of the firstcompute instance; and prevent transmission of the third frame via thefirst port.
 3. The network virtualization device of claim 1, wherein theplurality of ports further comprises a second port connected with asecond host machine hosting a second compute instance, the secondcompute instance being a second member of the virtual L2 network,wherein the execution of the instructions further configures the networkvirtualization device to: generate a second L2 BPDU by applying a secondloop detection protocol specific to only the second port and the secondhost machine; transmit, to the second compute instance via the secondport, a third frame that includes the second L2 BPDU; determine that thesecond L2 BPDU is not received back from the second compute instance;and determine that no loop exists between the network virtualizationdevice and the second compute instance.
 4. The network virtualizationdevice of claim 3, wherein the execution of the instructions furtherconfigures the network virtualization device to: receive a fourth framethat comprises a MAC address of the second compute instance as adestination address; and transmit the fourth frame via the second portresponsive to determining that no loop exists.
 5. The networkvirtualization device of claim 1, wherein the execution of theinstructions further configures the network virtualization device to:receive a third frame via the second port, the third frame comprising afirst media access control (MAC) address of the second compute instanceas a source address, a second MAC address of a third compute instance asa destination address, and an L2 protocol data unit (PDU), the thirdcompute instance being a member of the virtual L2 network; determinethat a loop prevention rule prevents transmission of a frame using aport via which the frame was received; determine that the third frame isto be transmitted via all ports of the network virtualization devicebased on the second MAC address; and transmit the third frame via allports of the network virtualization device except the second port basedon the loop prevention rule.
 6. The network virtualization device ofclaim 1, wherein generating the first L2 BPDU is triggered by framecongestion to, from, or to and from the first compute instance exceeds acongestion level.
 7. The network virtualization device of claim 1,wherein generating the first L2 BPDU is triggered periodically.
 8. Amethod comprising: generating a first Layer 2 (L2) bridge protocol dataunit (BPDU) by applying a first loop detection protocol specific to onlya first port from a plurality of ports and a first host machineassociated with a network virtualization device, the networkvirtualization device including the plurality of ports, the first portconnected with the first host machine, the first host machine hosting afirst compute instance, the first compute instance being a first memberof a virtual L2 network; transmitting, to the first compute instance viathe first port, a first frame that includes the first L2 BPDU;receiving, from the first compute instance via the first port, a secondframe; determining that the second frame comprises the first L2 BPDU;and determining that a loop exists between the network virtualizationdevice and the first compute instance based on the first loop detectionprotocol and the first L2 BPDU of the second frame.
 9. The method ofclaim 8, further comprising: disabling the first port based on the loop;receiving a third frame that comprises a MAC address of the firstcompute instance; and preventing transmission of the third frame via thefirst port.
 10. The method of claim 8, further comprising: generating asecond L2 BPDU by applying a second loop detection protocol specific toonly a second port of the plurality of ports and a second host machine,the second host machine hosting a second compute instance, the secondcompute instance being a second member of the virtual L2 network;transmitting, to the second compute instance via the second port, athird frame that includes the second L2 BPDU; determining that thesecond L2 BPDU is not received back from the second compute instance;and determining that no loop exists between the network virtualizationdevice and the second compute instance.
 11. The method of claim 10,further comprising: receiving a fourth frame that comprises a MACaddress of the second compute instance as a destination address; andtransmitting the fourth frame via the second port responsive todetermining that no loop exists.
 12. The method of claim 8, furthercomprising: receiving a third frame via the second port, the third framecomprising a first media access control (MAC) address of the secondcompute instance as a source address, a second MAC address of a thirdcompute instance as a destination address, and an L2 protocol data unit(PDU), the third compute instance being a member of the virtual L2network; determining that a loop prevention rule prevents transmissionof a frame using a port via which the frame was received; determiningthat the third frame is to be transmitted via all ports of the networkvirtualization device based on the second MAC address; and transmittingthe third frame via all ports of the network virtualization deviceexcept the second port based on the loop prevention rule.
 13. The methodof claim 8, wherein generating the first L2 BPDU is triggered by framecongestion to, from, or to and from the first compute instance exceeds acongestion level.
 14. One or more non-transitory computer-readablestorage media storing instructions that, upon execution by one or moreprocessors of a network virtualization device, cause the networkvirtualization device to perform operations comprising: generating afirst Layer 2 (L2) bridge protocol data unit (BPDU) by applying a firstloop detection protocol specific to only a first port from a pluralityof ports and a first host machine associated with the networkvirtualization device, the network virtualization device including theplurality of ports, the first port connected with the first hostmachine, the first host machine hosting a first compute instance, thefirst compute instance being a first member of a virtual L2 network;transmitting, to the first compute instance via the first port, a firstframe that includes the first L2 BPDU; receiving, from the first computeinstance via the first port, a second frame; determining that the secondframe comprises the first L2 BPDU; and determining that a loop existsbetween the network virtualization device and the first compute instancebased on the first loop detection protocol and the first L2 BPDU of thesecond frame.
 15. The one or more non-transitory computer-readablestorage media of claim 14, wherein the operations further comprise:disabling the first port based on the loop; receiving a third frame thatcomprises a MAC address of the first compute instance; and preventingtransmission of the third frame via the first port.
 16. The one or morenon-transitory computer-readable storage media of claim 14, wherein theoperations further comprise: generating a second L2 BPDU by applying asecond loop detection protocol specific to only a second port of theplurality of ports and a second host machine, the second host machinehosting a second compute instance, the second compute instance being asecond member of the virtual L2 network; transmitting, to the secondcompute instance via the second port, a third frame that includes thesecond L2 BPDU; determining that the second L2 BPDU is not received backfrom the second compute instance; and determining that no loop existsbetween the network virtualization device and the second computeinstance.
 17. The one or more non-transitory computer-readable storagemedia of claim 16, wherein the operations further comprise: receiving afourth frame that comprises a MAC address of the second compute instanceas a destination address; and transmitting the fourth frame via thesecond port responsive to determining that no loop exists.
 18. The oneor more non-transitory computer-readable storage media of claim 14,wherein the operations further comprise: receiving a third frame via thesecond port, the third frame comprising a first media access control(MAC) address of the second compute instance as a source address, asecond MAC address of a third compute instance as a destination address,and an L2 protocol data unit (PDU), the third compute instance being amember of the virtual L2 network; determining that a loop preventionrule prevents transmission of a frame using a port via which the framewas received; determining that the third frame is to be transmitted viaall ports of the network virtualization device based on the second MACaddress; and transmitting the third frame via all ports of the networkvirtualization device except the second port based on the loopprevention rule.
 19. The one or more non-transitory computer-readablestorage media of claim 14, wherein generating the first L2 BPDU istriggered by frame congestion to, from, or to and from the first computeinstance exceeds a congestion level.
 20. The one or more non-transitorycomputer-readable storage media of claim 14, wherein generating thefirst L2 BPDU is triggered periodically.